This document contains descriptions of various problems for practicing Java programming. Each problem is accompanied by a link to the corresponding class in which it can be solved and detailed instructions.
Task
The purpose of this exercise is to make you familiar with the Autocode platform. Estimated workload of this exercise is 5 minutes.
Please, proceed to HelloAutocode class
and write a simple program that prints "Hello, Autocode!" (don't print quote marks).
Task
The purpose of this exercise is to familiarize you with basic usage of standard input stream.
Estimated workload of this exercise is 5 minutes.
Please, proceed to the class MeetAStranger.
The program must read a string from System.in and print a message "Hello, input".
Note that when entering an input string consisting of several words, the entire input must be printed.
Input: Mrs. Robinson
Output: Hello, Mrs. Robinson
Task
The purpose of this exercise is to familiarize you with basic int operations.
Estimated workload of this exercise is 30 minutes.
Please, proceed to ElectronicWatch class.
The program must print an electronic watch screen output for a given value of seconds since midnight.
Input value is given via System.in. Output value must be printed to System.out
It is guaranteed, that input number is non-negative.
Output format is h:mm:ss (possible values: [0:00:00; 23:59:59]).
Extra challenge: try to solve the task without using if statements or cycles.
Input: 60
Output: 0:01:00
Input: 3599
Output: 0:59:59
Input: 86229
Output: 23:57:09
Input: 86400
Output: 0:00:00
Input: 89999
Output: 0:59:59
Input: 86460
Output: 0:01:00
Task
The purpose of this exercise is to familiarize you with simple conditional statements.
Estimated workload of this exercise is 20 min.
Please, proceed to MeetAnAgent class
and write a program that:
- asks for an input number,
- if the input equals to the secret password number, prints "Hello, Agent",
- otherwise, prints "Access denied"
Secret password is stored in final static int PASSWORD.
Input: 133976
Output: Hello, Agent
Input: 711
Output: Access denied
Task
The purpose of this exercise is to train you in usage of simple cycles and conditional statements.
Estimated workload of this exercise is 20 min.
Please, proceed to HelloStrangers class
and write a program that:
- asks for a number - amount of strangers to meet,
- then reads stranger names line by line
- and, finally, prints line by line "Hello, stranger name" for each stranger.
It is guaranteed that the input is not null. It is guaranteed that the input of strangers count is int number.
Consider special cases:
- If strangers count is zero, then program must print "Oh, it looks like there is no one here".
- If strangers count is negative, then program must print "Seriously? Why so negative?".
Hint: In case you use the Scanner class, it might be helpful sure to check strings it reads be non-empty.
Input:
3
Athos
Porthos
Aramis
Output:
Hello, Athos
Hello, Porthos
Hello, Aramis
Input:
0
Output:
Oh, it looks like there is no one here
Input:
-3
Output:
Seriously? Why so negative?
Task
The purpose of this exercise is to train you in usage of simple integer operations.
Estimated workload of this exercise is 30 min.
Consider a snail travels up a tree a feet each day. Then snail slides down b feet each night. Height of the tree is h feet.
Please, proceed to Snail class
and write a program that prints number of days for the snail to reach the top of the tree.
Program reads a, b, h line by line. Input values are guaranteed to be positive integers.
If the snail cannot reach the top of the tree, print the message Impossible.
Input:
4
2
14
Output:
6
Input:
4
3
10
Output:
7
Input:
4
4
10
Output:
Impossible
Input:
4
4
1
Output:
1
Task
The purpose of this exercise is to familiarize you with basic conditional and cyclic operations.
Estimated workload of this exercise is 20 minutes.
Consider a company of friends visiting a restaurant. They decided to equally split the bill.
Friends decided to add 10 percent of the bill total amount as tips. Then they cover the total payment in equal parts.
Please, proceed to GoDutch class
and write a program that reads a bill total amount and a number of friends, and then prints part to pay.
Consider some details:
- Program must read data from System.in
- Bill total amount cannot be negative. If input value is negative, the program stops, printing:
Bill total amount cannot be negative - Number of friends cannot be negative or zero. If input value is, then the program stops, printing:
Number of friends cannot be negative or zero - Bill total amount, number of friends and part to pay are integers
Input:
1000
5
Output:
220
Task
The purpose of this exercise is to train you to use simple loops and conditional statements.
Estimated workload of this exercise is 20 min.
Please, proceed to FindMaxInSeq
and write a program that reads a sequence of integer values from standard output and finds the maximum value. You must
place your solution into the max method to pass tests.
Details:
- You must read sequence values until the next one is
0. Zero value means end of the input sequence. - The sequence is guaranteed to contain at least one value.
Input:
2 4 6 9 2 4 5 0
Output:
9
Task
The purpose of this exercise is to train you to use simple loops and conditional statements.
Estimated workload of this exercise is 20 min.
Please, proceed to Average class
and write a program that reads a sequence of integer values from standard input and finds the average value.
Details:
- You must read sequence values until the next one is
0. Zero value means end of the input sequence. - The sequence is guaranteed to contain at least one value.
- Average value is also an integer. Use integer operations.
Input: 1 2 3 4 5 0
Output: 3
Input: 1 2 3 4 6 0
Output: 3
Input: 1 2 3 4 0
Output: 2
Input: 1 1 9 0
Output: 3
Task
The purpose of this exercise is to familiarize you with basic conditional and cyclic operations.
Estimated workload of this exercise is 20 minutes.
Please, proceed to PizzaSplit class.
The program must read two values from System.in:
- number of people;
- number of pieces per pizza.
It is guaranteed that this values are positive integers.
Then the program must print the minimum number of pizzas (not zero) so that everyone has an equal number of slices and no slice is left.
Input: 12 8
Output: 3
Task
The purpose of this exercise is to train you to design programs that need decision trees.
Estimated workload of this exercise is 30 min.
Please, proceed to the QuadraticEquation class and implement a program to solve quadratic equations.
For the given quadratic equation coefficients (ax2 + bx + c = 0), return one or two roots of the equation if there is any in the set of real numbers.
Input value is given via System.in. Output value must be printed to System.out.
Output format is:
- "x1 x2" (two roots in any order separated by space) if there are two roots,
- "x" (just the value of the root) if there is the only root,
- "no roots" (just a string value "no roots") if there is no root.
The a parameter is guaranteed to be not zero.
Hint: Quadratic formula reference
Input: 1 -2 1
Output: 1
Input: 2 5 -3
Output: -3 0.5
Input: 2 2 2
Output: no roots
Task
The purpose of this exercise is to train you to work with arrays.
Estimated workload of this exercise is 20 min.
Please, proceed to the MaxMethod class
and implement the max method.
The correct implementation should receive an array of int values and return its maximum value.
Details:
- An input array is guaranteed to not be an empty array or
null. maxmethod must not modify the array.- Input array may contain any
intvalue betweenInteger.MIN_VALUEandInteger.MAX_VALUE.
int[] vals = new int[]{-2, 0, 10, 5};
int result = MaxMethod.max(vals);
System.out.println(result == 10); // trueTask
The purpose of this exercise is to train you to work with arrays.
Estimated workload of this exercise is 20 min.
Please, proceed to the SumOfEvenNumbers class and
implement the sum method.
The correct implementation should receive an array of int values and return the sum of even numbers.
Details:
- If given array is null or empty, method returns 0.
summethod must not modify the array.- Input array may contain any
intvalue betweenInteger.MIN_VALUEandInteger.MAX_VALUE.
int[]vals = new int[]{-2,10,0,5};
int result = SumOfEvenNumbers.sum(vals);
System.out.println(result == 8); // trueTask
The purpose of this exercise is to train you to work with arrays.
Estimated workload of this exercise is 20 min.
Please, proceed to SumOfPrevious class
and implement getSumCheckArray method.
The correct implementation should receive an array of int values
and return an array of booleans where each element is a result
of a check if a corresponding element is a sum
of two previous elements in given array.
Details:
- The length of given array is guaranteed to be 2 or more.
- Given array is guaranteed to be not null.
- Method returns an array of booleans where each element is a result for corresponding element in given array.
- First two elements of the boolean array are always false.
Input array: [1, -1, 0, 4, 6, 10, 15, 25]
Output array: [false, false, true, false, false, true, false, true]
Task
The purpose of this exercise is to train you to work with arrays.
Estimated workload of this exercise is 30 min.
Please, proceed to the LocalMaximaRemove class and
implement the removeLocalMaxima method.
The correct implementation should receive an array of int values
and return a copy of a given array with all local maxima removed in it.
The original array must not be changed.
Local maximum is an element that is bigger that any of its neighbour elements. You should remove elements that are local maxima in the original array.
Details:
- The size of given array is guaranteed to be more than 1.
- Given array is guaranteed to be not null.
- If the array has no local maxima, then you should return its copy without changes.
- You may use java.util.Arrays.* methods.
Input array: [18, 1, 3, 6, 7, -5]
Output array: [1, 3, 6, -5]
Task
The purpose of this exercise is to train you to work with arrays.
Estimated workload of this exercise is 30 min.
Please, proceed to CycleSwap class
and implement its static methods:
-
void cycleSwap(int[] array)
Shifts all the elements in the given array to the right by 1 position.
In this case, the last array element becomes first.
For example,1 3 2 7 4becomes4 1 3 2 7. -
void cycleSwap(int[] array, int shift)
Shift all the elements in the given array to the right in the cycle manner byshiftpositions.
Shift value is guaranteed to be non-negative and not bigger than the array length.
For example,1 3 2 7 4with a shift of3becomes2 7 4 1 3.
For a greater challenge, try not using loops in your code (not mandatory).
Note that input array may be empty.
Code Sample:
...
int[] array = new int[]{1, 3, 2, 7, 4};
CycleSwap.cycleSwap(array);
System.out.println(Arrays.toString(array));Output:
[4, 1, 3, 2, 7]
Code Sample:
...
int[] array = new int[]{1, 3, 2, 7, 4};
CycleSwap.cycleSwap(array, 2);
System.out.println(Arrays.toString(array));Output:
[7, 4, 1, 3, 2]
Code Sample:
...
int[] array = new int[]{1, 3, 2, 7, 4};
CycleSwap.cycleSwap(array, 5);
System.out.println(Arrays.toString(array));Output:
[1, 3, 2, 7, 4]
Task
The purpose of this exercise is to train you to work with arrays.
Estimated workload of this exercise is 45 min.
Please, proceed to Spiral class and implement its static method:
int[][] spiral(int rows, int columns)
Return a two-dimensional array coming in the form of a table and containing numbers from1up torows * columns. The size of the table will be specified by the given parameters.
Numbers fill the "table" clockwise from the top-level corner in a spiral manner.
For example, for parameter values(3, 4), the output array should be:1 2 3 4 10 11 12 5 9 8 7 6
Code Sample:
...
int[][] spiral = Spiral.spiral(3, 4);
for (int i = 0; i < spiral.length; i++) {
for (int j = 0; j < spiral[i].length; j++) {
System.out.print(String.format("%4s", spiral[i][j]));
}
System.out.println();
}Output:
1 2 3 4
10 11 12 5
9 8 7 6
Code Sample:
...
int[][] spiral = Spiral.spiral(4, 3);
for (int i = 0; i < spiral.length; i++) {
for (int j = 0; j < spiral[i].length; j++) {
System.out.print(String.format("%4s", spiral[i][j]));
}
System.out.println();
}Output:
1 2 3
10 11 4
9 12 5
8 7 6
Code Sample:
...
int[][] spiral = Spiral.spiral(5, 6);
for (int i = 0; i < spiral.length; i++) {
for (int j = 0; j < spiral[i].length; j++) {
System.out.print(String.format("%4s", spiral[i][j]));
}
System.out.println();
}Output:
1 2 3 4 5 6
18 19 20 21 22 7
17 28 29 30 23 8
16 27 26 25 24 9
15 14 13 12 11 10
Code Sample:
...
int[][] spiral = Spiral.spiral(5, 5);
for (int i = 0; i < spiral.length; i++) {
for (int j = 0; j < spiral[i].length; j++) {
System.out.print(String.format("%4s", spiral[i][j]));
}
System.out.println();
}Output:
1 2 3 4 5
16 17 18 19 6
15 24 25 20 7
14 23 22 21 8
13 12 11 10 9
Task
The purpose of this exercise is to train you to work with arrays.
Estimated workload of this exercise is 45 min.
Please, proceed to TransposeMatrix
class an implement its method multiply.
It takes a rectangular integer array (matrix) as a parameter and returns it transposed.
Consider an integer matrix represented as a rectangular array. The task is to transpose a given matrix over its main diagonal. The transposition of a matrix over its main diagonal is simply a flipped version of the original matrix.
Hint: Transpose Reference
Input:
{
{0, 1, 2},
{3, 4, 5},
{6, 7, 8}
}
Output:
{
{0, 3, 6},
{1, 4, 7},
{2, 5, 8}
}
Task
The purpose of this exercise is to train you to work with arrays.
Estimated workload of this exercise is 60 min.
Please, proceed to MultiplyMatrix
class and implement its multiply method.
It takes two rectangular integer arrays (matrices) and returns the result of their multiplication.
Consider two integer matrices represented as rectangular arrays. The task is to multiply given matrices. The definition of matrix multiplication indicates a row-by-column multiplication, where the entries in the i-th row of A are multiplied by the corresponding entries in the j-th column of B and then the ij-th element of the resulting matrix is the sum of that multiplication results.
Note that it is guaranteed that the number of columns in the first matrix is equal to the number of rows in the second matrix.
Input:
{{1, 2, 3},
{4, 5, 6}},
{{7 , 8 },
{9 , 10},
{11, 12}}
Output:
{{58 , 64 },
{139, 154}}
Task
The purpose of this exercise is to train you to work with classes and methods.
Estimated workload of this exercise is 45 min.
Please, implement the method intersection(Line) in class Line.
It must return a Point of intersection of two lines.
Note that lines are defined by linear equations: y = k * x + b.
Line constructor takes k and b coefficients as parameters.
If lines coincide or do not intersect, the method must return null.
It may seem surprising that we use int for arguments and fields of coordinates.
The point is that using double will bring some extra complexity we want to avoid for this basic exercise.
All tests are selected in to induce calculations without remainders.
You may check your result in class Main.
public class Main {
public static void main(String[] args) {
Line line1 = new Line(1,1);
Line line2 = new Line(-1,3);
System.out.println(line1.intersection(line2)); // (1;2)
}
}Task
The purpose of this exercise is to train you to work with classes and methods.
Estimated workload of this exercise is 45 min.
Please, implement the following methods of class Segment:
- constructor with start and end points as parameters
Ensure that a created segment exists and is not degenerative which means that the start and the end of the segment is not the same point.
If it is, usethrow new IllegalArgumentException()to raise an error. double length()
Return length of the segment.Point middle()
Return a middle point of the segment.Point intersection(Segment another)
Return a point of the intersection of the current segment and the given one.
Returnnullif there is no such point.
Returnnullif segments are collinear.
Please, note that intersection point must lay on both segments.
Class Point is already there.
Hints:
You may use Main class to try your code.
There are some examples below.
Sample code:
...
double length = new Segment(new Point(0, 0), new Point(3, 4)).length();
System.out.println(length);Output: 5
Sample code:
...
Segment first = new Segment(new Point(0, 0), new Point(4, 4));
Segment second = new Segment(new Point(2, 0), new Point(0, 2));
Point intersection = first.intersection(second);
System.out.println(intersection.getX());
System.out.println(intersection.getY());Output:
1
1
Sample code:
...
Segment segment = new Segment(new Point(2, 0), new Point(0, 2));
Point midpoint = segment.middle();
System.out.println(midpoint.getX());
System.out.println(midpoint.getY());Output:
1
1
Sample code:
...
Segment first = new Segment(new Point(0, 0), new Point(4, 0));
Segment second = new Segment(new Point(2, 1), new Point(1, 2));
Point intersection = first.intersection(second);
System.out.println(intersection == null);Output:
true
Task
The purpose of this exercise is to train you to work with classes and methods.
Estimated workload of this exercise is 45 min.
Please, implement methods of class Triangle:
- constructor, which has three points as parameters.
Consider these points as vertices of the triangle.
Ensure that the created triangle exists, and it is not degenerative.
If it is, usethrow new IllegalArgumentException()to raise an error. double area()
Return the area of the triangle.Point centroid()
Return the centroid of the triangle.
Class Point is already there.
Hints:
Please note that you may benefit from introducing more classes.
Sample code:
...
new Triangle(new Point(0,0), new Point(1, 0), new Point(2, 0));Result: Exception because such a triangle would be degenerative.
Sample code:
...
double area = new Triangle(new Point(0,0), new Point(3, 0), new Point(0, 4)).area();
System.out.println(area);Output:
6
Sample code:
...
Point centroid = new Triangle(new Point(0,0), new Point(3, 0), new Point(0, 3)).centroid();
System.out.println(centroid.getX());
System.out.println(centroid.getY());Output:
1
1
Task
The purpose of this exercise is to train you designing simple classes and their relations.
Estimated workload of this exercise is 2h.
Decrementing Carousel is a container, accepting int elements.
DecrementingCarousel has a maximum capacity, specified via the constructor.
When created, DecrementingCarousel is in accumulating state: you may add elements via the addElement method and can produce a CarouselRun object via the run method.
Once the run method is called, DecrementingCarousel is in running state: it refuses adding more elements.
The CarouselRun allows to iterate over elements of the carousel decrementing them one by one with the next method.
The next returns the value of the current element:
Then it decreases the current element by one and switches to the next element:
The CarouselRun iterates over elements in the order of their insertion.
When an element is decreased to zero, the CarouselRun will skip it in further iterations.
When there are no more elements available for decrementing, the CarouselRun returns -1.
The CarouselRun also has the isFinished method, which indicates, if the carousel has run out of the elements to decrement.
DecrementingCarousel has two public methods:
boolean addElement(int element)- adds an element. If element is negative or zero, do not add the element. If container is full, do not add the element. If therunmethod was called to create aCarouselRun, do not add the element. If element is added successfully, returntrue. Returnfalseotherwise.CarouselRun run()- returns aCarouselRunto iterate over the elements. If therunmethod has already been called earlier, it must returnnull:DecrementingCarouselmay generate only oneCarouselRunobject.
CarouselRun has two public methods:
int next()- returns the current value of the current element, then decreases the current element by one and switches to the next element in insertion order. Skips zero elements. When there is no more elements to decrease, returns-1.boolean isFinished()- when there is no more elements to decrease, returnstrue. Otherwise, returnsfalse.
Empty case:
CarouselRun run = new DecrementingCarousel(7).run();
System.out.println(run.isFinished()); //true
System.out.println(run.next()); //-1Regular case:
DecrementingCarousel carousel = new DecrementingCarousel(7);
carousel.addElement(2);
carousel.addElement(3);
carousel.addElement(1);
CarouselRun run = carousel.run();
System.out.println(run.isFinished()); //false
System.out.println(run.next()); //2
System.out.println(run.next()); //3
System.out.println(run.next()); //1
System.out.println(run.next()); //1
System.out.println(run.next()); //2
System.out.println(run.next()); //1
System.out.println(run.isFinished()); //true
System.out.println(run.next()); //-1Refusing adding more elements case:
DecrementingCarousel carousel = new DecrementingCarousel(3);
System.out.println(carousel.addElement(-2)); //false
System.out.println(carousel.addElement(0)); //false
System.out.println(carousel.addElement(2)); //true
System.out.println(carousel.addElement(3)); //true
System.out.println(carousel.addElement(1)); //true
//carousel is full
System.out.println(carousel.addElement(2)); //false
CarouselRun run = carousel.run();
System.out.println(run.next()); //2
System.out.println(run.next()); //3
System.out.println(run.next()); //1
System.out.println(run.next()); //1
System.out.println(run.next()); //2
System.out.println(run.next()); //1
System.out.println(run.isFinished()); //true
System.out.println(run.next()); //-1Refusing to add more elements after "run" was called:
DecrementingCarousel carousel = new DecrementingCarousel(10);
System.out.println(carousel.addElement(2)); //true
System.out.println(carousel.addElement(3)); //true
System.out.println(carousel.addElement(1)); //true
carousel.run();
System.out.println(carousel.addElement(2)); //false
System.out.println(carousel.addElement(3)); //false
System.out.println(carousel.addElement(1)); //falseRefusing to create more than one CarouselRun:
DecrementingCarousel carousel = new DecrementingCarousel(10);
System.out.println(carousel.run() == null); //false
System.out.println(carousel.run() == null); //trueTask
The purpose of this exercise is to train you to use extend classes with extends keyword.
Estimated workload of this exercise is 30 min.
Note, that if you have not done the "Decrementing Carousel" exercise,
you have to implement DecrementingCarousel and CarouselRun classes.
In this exercise you need to extend DecrementingCarousel.
You need to implement HalvingCarousel.
This subclass must halve elements instead of decrementing it by one.
Note that you need to apply regular integer division, discarding the remainder.
For example, 5 / 2 = 2.
Empty case:
CarouselRun run = new HalvingCarousel(7).run();
System.out.println(run.isFinished()); //true
System.out.println(run.next()); //-1Regular case:
DecrementingCarousel carousel = new HalvingCarousel(7);
carousel.addElement(20);
carousel.addElement(30);
carousel.addElement(10);
CarouselRun run = carousel.run();
System.out.println(run.isFinished()); //false
System.out.println(run.next()); //20
System.out.println(run.next()); //30
System.out.println(run.next()); //10
System.out.println(run.next()); //10
System.out.println(run.next()); //15
System.out.println(run.next()); //5
System.out.println(run.next()); //5
System.out.println(run.next()); //7
System.out.println(run.next()); //2
System.out.println(run.next()); //2
System.out.println(run.next()); //3
System.out.println(run.next()); //1
System.out.println(run.next()); //1
System.out.println(run.next()); //1
System.out.println(run.isFinished()); //true
System.out.println(run.next()); //-1Task
The purpose of this exercise is to train you to use extend classes with extends keyword.
Estimated workload of this exercise is 30 min.
Note, that if you have not done the "Decrementing Carousel" exercise,
you have to implement DecrementingCarousel and CarouselRun classes.
In this exercise you need to extend DecrementingCarousel.
You need to implement GraduallyDecreasingCarousel.
This subclass must decrement elements by gradually increasing decrement.
When you need to decrement an element for the first time, decrease it by 1.
Next time you need to decrement the same element, decrease it by 2.
Next time decrease by 3, then by 4 and so on.
Remember that you must not make process non-positive elements.
Empty case:
CarouselRun run = new GraduallyDecreasingCarousel(7).run();
System.out.println(run.isFinished()); //true
System.out.println(run.next()); //-1Regular case:
DecrementingCarousel carousel = new GraduallyDecreasingCarousel(7);
carousel.addElement(20);
carousel.addElement(30);
carousel.addElement(10);
CarouselRun run = carousel.run();
System.out.println(run.isFinished()); //false
System.out.println(run.next()); //20
System.out.println(run.next()); //30
System.out.println(run.next()); //10
System.out.println(run.next()); //19
System.out.println(run.next()); //29
System.out.println(run.next()); //9
System.out.println(run.next()); //17
System.out.println(run.next()); //27
System.out.println(run.next()); //7
System.out.println(run.next()); //14
System.out.println(run.next()); //24
System.out.println(run.next()); //4
System.out.println(run.next()); //10
System.out.println(run.next()); //20
System.out.println(run.next()); //5
System.out.println(run.next()); //15
System.out.println(run.next()); //9
System.out.println(run.next()); //2
System.out.println(run.isFinished()); //true
System.out.println(run.next()); //-1Task
The purpose of this exercise is to train you to use extend classes with extends keyword.
Estimated workload of this exercise is 30 min.
Note, that if you have not done the "Decrementing Carousel" exercise,
you have to implement DecrementingCarousel and CarouselRun classes.
In this exercise you need to extend DecrementingCarousel.
You need to implement DecrementingCarouselWithLimitedRun.
This subclass must decrement elements as a usual DecrementingCarousel.
The difference is that this implementation must produce a carousel run,
which limits number of calls to the next method.
When the limit of calls reached carousel run must consider itself finished.
Empty case:
CarouselRun run = new DecrementingCarouselWithLimitedRun(7, 5).run();
System.out.println(run.isFinished()); //true
System.out.println(run.next()); //-1Regular case:
DecrementingCarousel carousel = new DecrementingCarouselWithLimitedRun(7, 10);
carousel.addElement(20);
carousel.addElement(30);
carousel.addElement(10);
CarouselRun run = carousel.run();
System.out.println(run.isFinished()); //false
System.out.println(run.next()); //20
System.out.println(run.next()); //30
System.out.println(run.next()); //10
System.out.println(run.next()); //19
System.out.println(run.next()); //29
System.out.println(run.next()); //9
System.out.println(run.next()); //18
System.out.println(run.next()); //28
System.out.println(run.next()); //8
System.out.println(run.next()); //17
System.out.println(run.isFinished()); //true
System.out.println(run.next()); //-1Task
The purpose of this exercise is to train basic inheritance features.
Estimated workload of this exercise is 120 min.
In this exercise we are going to manage business logic of planning a sprint. A sprint is the basic unit of software development in SCRUM. Sprints are time boxed. Time capacity of a sprint is agreed while planning. Then we consider a sprint to be filled with some tasks.
We consider a task to be implemented with general-purpose Ticket class.
But we also consider a sprint to accept only subtypes of the Ticket class: Bug and UserStory.
Here is a diagram depicting the public interface of these classes and their relations:
Here are API details:
Ticket
Every ticket has an id, a name and an estimate of hours to complete it. One provides them via the constructor of theTicketclass. Also, a ticket may be completed or not. When a ticket is created, it is not completed.getId()- Returns the id of the ticket.getName()- Returns the name of the ticket.getEstimate()- Returns the estimate of the ticket.isCompleted()- Returnstrueif the ticket is completed,falseotherwise.complete()- Sets the ticket to completed state.
UserStory
We consider a user story to be a ticket that may contain some dependencies. A dependency is another user story that must be completed first to allow the dependent user story to complete. One provides dependencies of the UserStory via the constructor of theUserStoryclass.complete()- Like theTicket#complete()method, this sets the ticket to completed state. The difference is that the user story may not be completed if its dependencies are not completed yet.getDependencies()- Returns a defensive copy of dependencies array.toString()- Returns a String representing this user story, using its id and name. Example: "[US 1] User Registration Entity"
Bug
We consider a bug to be a ticket, that is related to some completed user story. Bugs may not exist by their on, without a related user story.createBug(int id, String name, int estimate, UserStory userStory)- A static method to create a Bug instance.
Returnsnullif the related user story isnullor is not completed. Otherwise, returns a created Bug instance.toString()- Returns a String representing this bug, using its id, name and the name of the related user story.
Example: with id = 2, name = "Add password repeat" and the related user story name = "Registration Form" the resulting string would be "[Bug 2] Registration Form: Add password repeat"
Sprint
Sprints has the time capacity and the tickets limit, specified via constructor. It is not allowed for a Sprint to contain tickets with total estimate greater than time capacity. It is not allowed for a Sprint to contain total amount of tickets greater than tickets limit.
We consider a sprint to accept tickets viaadd*methods. That methods returntruewhen an input ticket was accepted andfalseotherwise. Note that we consider a sprint to not accept:nullvalues,- tickets, that are already completed
- tickets, that has an estimate value that will lead to capacity overflow if added
- any ticket, if the sprint ticket limit is reached.
addUserStory(UserStory userStory)- accepts a userStory, if it is notnull, not completed and its uncompleted dependencies are already accepted to the sprint. Returnstrueif the user story is accepted,falseotherwise.addBug(Bug bugReport)- accepts a bug, if it is notnulland not completed. Returnstrueif the bug is accepted,falseotherwise.getTickets()- Returns a defensive copy of the array of the sprint tickets. Make sure the order of tickets is as they were accepted to the sprint.getTotalEstimate()- Returns the sum of estimates of all the tickets accepted to the sprint.
Important restriction: Note that in this exercise you may not use Collections and Streams.
Wikipedia on the Scrum Sprint: https://en.wikipedia.org/wiki/Scrum_(software_development)#Sprint
Task
The purpose of this exercise is to train you designing simple interface implementations and use them.
Estimated workload of this exercise is 2h.
In this exercise you need to design two implementations of the Task interface:
CountDownTask:- The constructor of
CountDownTasktakes a single int value as a parameter. It is the initial value of the countdown. Input value must not be negative. If it is, set zero value. - Each time the
executemethod is called, this value decrements by one, until it reaches zero. Then theexecutemethod no longer decrements the value and the task is considered finished. - If the task is initialized with zero value, consider it finished right upon creating.
- Value of the task is accessible via getter.
- The constructor of
CompleteByRequestTask:- Constructor of the
CompleteByRequestTasktakes no parameters. - Calling
executemethod on the task does not make it finished until thecompletemethod is called. - Once the
completemethod is called, the next call toexecutemakes the task finished. Note that the task is not finished right after calling thecompletemethod. The task finishes only when subsequent call toexecuteoccurs.
- Constructor of the
Also, you need to implement the TaskCarousel:
- A task carousel has a capacity provided as a constructor parameter.
- The
TaskCarouselhasisEmptymethod. It returnstrueif there is no task in the carousel for execution. Returnsfalseotherwise. - The
TaskCarouselhasisFullmethod. It returnstrueif there is no more room in the carousel to add another task. Returnsfalseotherwise. - You may add tasks to the carousel via
addTaskmethod. It returnstrueif the task is accepted andfalseotherwise. Task may be not accepted due to following reasons:- Task argument is null.
- Task is already finished.
- Carousel is full.
- You may execute tasks in the carousel via
executemethod.- Each time when this method is invoked, carousel must switch to the next task within and execute it.
- Iteration is in circular manner.
If there are 4 tasks inside a carousel,
then if we call
executemethod on the carousel 4 times in a row, each task must be executed once. - If the task is finished after execution, remove it from the carousel.
- The method returns
trueif any task was executed. Returnsfalseotherwise.
Single task case:
TaskCarousel carousel = new TaskCarousel(4);
System.out.println(carousel.isEmpty()); //true
System.out.println(carousel.isFull()); //false
System.out.println(carousel.execute()); //false
CountDownTask task = new CountDownTask(2);
System.out.println(carousel.addTask(task)); //true
System.out.println(carousel.isEmpty()); //false
System.out.println(carousel.isFull()); // false
System.out.println(task.getValue()); //2
System.out.println(carousel.execute()); //true
System.out.println(task.getValue()); //1
System.out.println(carousel.execute()); //true
System.out.println(task.getValue()); //0
System.out.println(carousel.execute()); //false
System.out.println(carousel.isEmpty()); //trueThree tasks case:
TaskCarousel carousel = new TaskCarousel(3);
CountDownTask task1 = new CountDownTask(2);
CountDownTask task2 = new CountDownTask(2);
CompleteByRequestTask task3 = new CompleteByRequestTask();
System.out.println(carousel.addTask(task1)); //true
System.out.println(carousel.addTask(task2)); //true
System.out.println(carousel.addTask(task3)); //true
System.out.println(carousel.isFull()); // true
for(int i = 0; i < 100; i++){
System.out.println(carousel.execute()); // true
}
System.out.println(task1.isFinished()); // true
System.out.println(task2.isFinished()); // true
System.out.println(task3.isFinished()); // false
task3.complete();
System.out.println(task3.isFinished()); // false
System.out.println(carousel.execute()); // true
System.out.println(task3.isFinished()); // true
System.out.println(carousel.isEmpty()); // trueTask
The purpose of this exercise is to train you to work with classes, methods and inheritance.
Estimated workload of this exercise is 60 min.
Please, make Triangle,
Quadrilateral,
Circle classes
extend Figure abstract class.
Implement methods in Triangle, Quadrilateral, Circle:
- constructors with following parameters:
Triangle- three vertices (points) as parameters.Quadrilateral- four vertices (points) as parameters.Circle- point of the center anddoublevalue of the radius.
All the input datasets in tests are guaranteed to form a non-degenerative figures. For Quadrilaterals, it is guaranteed that all test datasets would form a convex quadrilaterals.
-
public double area()
Return the area of the figure.
Note: Convex quadrilaterals can be divided into two triangles by any of their diagonals. -
public String pointsToString()
Return a String value in following formats:
Triangle-- Format:
(a.x,a.y)(b.x,b.y)(c.x,c.y) - Example:
(0.0,0.0)(0.1,5.8)(7.0,7.0)
- Format:
Quadrilateral-- Format:
(a.x,a.y)(b.x,b.y)(c.x,c.y)(d.x, d.y) - Example:
(0.0,0.0)(0.0,7.1)(7.0,7.0)(7.0,0.0)
- Format:
Circle-- Format:
(center.x,center.y) - Example:
(0.0,0.6)
- Format:
Note:: you may benefit from implementing toString() in the Point class
public String toString()
Return a String value in following formats:
Triangle-- Format:
Triangle[(a.x,a.y)(b.x,b.y)(c.x,c.y)] - Example:
Triangle[(0.0,0.0)(0.1,5.8)(7.0,7.0)]
- Format:
Quadrilateral-- Format:
Quadrilateral[(a.x,a.y)(b.x,b.y)(c.x,c.y)(d.x, d.y)] - Example:
Quadrilateral[(0.0,0.0)(0.0,7.1)(7.0,7.0)(7.0,0.0)]
- Format:
Circle-- Format:
Circle[(center.x,center.y)radius] - Example:
Circle[(0.0,0.6)4.5]
- Format:
Note: you may use default implementation given in the Figure class, when it suits a case well.
public Point leftmostPoint()
Return a leftmost point of the figure: the one having the leastXcoordinate.
If there are many leftmost points, return any of them.
Point class is already there.
Hints:
- Degeneracy reference
- Convex quadrilateral reference
- Triangle area reference
- Circle area reference
- Quadrilateral area reference
You may use Main class to try your code.
There are some examples below.
Sample code:
...
double area = new Triangle(new Point(0,0), new Point(3, 0), new Point(0, 4)).area();
System.out.println(area);Output:
6
Sample code:
...
double area = new Quarilateral(new Point(1,0), new Point(2, 1), new Point(1, 2), new Point(0, 1)).area();
System.out.println(area);Output:
2
Sample code:
...
double area = new Circle(new Point(1,1), 3).area();
System.out.println(area);Output:
28.274333882308138
Task
The purpose of this exercise is to train you to work with classes, methods and inheritance.
Estimated workload of this exercise is 60 min.
Please, make Triangle,
Quadrilateral,
Circle classes
extend Figure abstract class.
Implement methods in Triangle, Quadrilateral, Circle:
- Constructors with following parameters:
-
Triangle- three vertices (points) as parameters. -
Quadrilateral- four vertices (points) as parameters. -
Circle- point of the center and double value of the radius.Ensure figures are not degenerative.
All of them must have non-zero area.
Quadrilateral is also must be convex.
If a figure is not good, throw an IllegalArgumentException.
Note: A non-degenerative convex quadrilateral is divided into four non-degenerative triangles by its diagonals. Note: double calculations are not completely accurate, use error delta, where applies.
public Point centroid()
Return the centroid of the figure.
Centroid refers to center of mass of the plain figure, not the baricenter.
In other words it should be "area centroid".public boolean isTheSame(Figure figure)
Two figures are considered to be the same only:
-
if they have the same type
-
and if they coincide (e.g. have same vertices).
Note: order of the vertices have not to be the same.
Note: double calculations are not completely accurate, use error delta, where applies.
Note for curious: it is almost like equals() but it is not. Method equals requires consistent behavior alongside hashCode() and it is quite complicated to establish in terms of approximate equality like in this exercise
Point class is already there.
You may use main method of Figure class to try out your code.
Hints:
Task
The purpose of this exercise is to train using nested classes.
Estimated workload of this exercise is 60 min.
In this exercise we are going to manage contacts information.
A Contact is a class containing
different information of how to reach a person or a company: phone number, emails, social media.
A contact has a name, which is provided via the class constructor. Also, a contact contains limited amount of entries:
- a phone number (only a single one)
- emails (up to 3 entries)
- social media links (up to 5 entries)
A contact info entry is described with ContactInfo interface.
Each entry has a title and a value.
You need to implemented them as nested classes of the Contact class:
Contact.NameContactInfo- AContactInfoimplementation providing the name of the contact. Implement as private non-static nested class. Use"Name"for the entry title. It must not have its own fields. It must use fields of the boundedContactinstance instead.Contact.Email- AContactInfoimplementation containing an email. Implement as public static nested class. Use"Email"for the entry title.Contact.Social- AContactInfoimplementation containing a social media link/id. Implement as public static nested class. Let the user of the class define the title.- Other implementations must be anonymous. Do not provide other non-anonymous classes.
It is possible to add contact info entries via add* methods.
All such methods return the created entry as the result, null if nothing was added to the contact.
addEmail(String localPart, String domain)
Adds an email entry.
addEmail("someone", "somewhere.com").getValue()will result tosomeone@somewhere.com.addEpamEmail(String firstname, String lastname)
Adds a special email entry with "epam.com" domain. Please, implement this method using an anonymous extension of theEmailclass. Use"Epam Email"for the entry title.
addEpamEmail("some", "one").getValue()will result tosome_one@epam.comaddPhoneNumber(int code, String number)
Adds a contact info entry for the phone number. Please, implement this method using an anonymous class. Use"Tel"for the entry title.
addPhoneNumber(44, "444 444-44-44").getValue()will result to+44 444 444-44-44addTwitter(String twitterId)
Adds a contact info entry for the Twitter social media id. Use"Twitter"for the entry title, the given id for the value.addInstagram(String instagramId)
Adds a contact info entry for the Instagram social media id. Use"Instagram"for the entry title, the given id for the value.addSocialMedia(String title, String id)
Adds a contact info entry for the generic social media id. Use the given title for the entry title, the given id for the value.
Note that it is possible to rename contact with the rename method.
Make sure it is not possible to rename contact to have null or empty value as the name.
One more method that the Contact class have is the getInfo() method.
This method returns an array containing the ContactInfo entries in the following order:
- name contact info
- phone number contact info (if set)
- email entries in order of addition (if any added)
- social media entries in order of addition (if any added) Resulting array must not contain any null values.
Important restriction: Note that in this exercise you may not use Collections and Streams.
Task
The purpose of this exercise is to train using nested classes.
Estimated workload of this exercise is 60 min.
In this exercise we are going to design a DSL of arithmetic expressions.
An Expression is an interface.
It describes two methods:
int evaluate()- returns the result of evaluating of the expression.String toExpressionString()- returns string representation of the expression.
The only non-anonymous implementation of the Expression is
the Variable class.
Please, implement its methods:
public Variable(String name, int value)- a constructor of theVariableclass. Sets name and value of the variable.public void setValue(int value)- a method to change the value of the variable.public int evaluate()- returns the value of the variable.public String toExpressionString()- returns the name of the variable.
All other implementations of the Expression interface must be anonymous, defined in static methods of
the Expressions class:
Variable var(String name, int value)- returns aVariablewith given name and value. A simple convenience method.Expression val(int value)- returns anExpressionholding a value. Consider following methods' implementation details:int evaluate()- returns the given value.String toExpressionString()- returns a string representation of the given value. Enclose with(,)braces if the value is negative.
Expression sum(Expression... members)- returns anExpressionholding a sum of the given members. Consider that it is guaranteed that at least two members will be given each method call. Consider following methods' implementation details:int evaluate()- returns the sum of evaluation result of all the given members.String toExpressionString()- returns a string representation of the given sum. Example:sum(val(1), val(2), val(3)).toExpressionString()results to(1 + 2 + 3).
Expression product(Expression... members)- returns anExpressionholding a product of the given members. Consider that it is guaranteed that at least two members will be given each method call. Consider following methods' implementation details:int evaluate()- returns the product of evaluation result of all the given members.String toExpressionString()- returns a string representation of the given product. Example:product(val(1), val(2), val(3)).toExpressionString()results to(1 * 2 * 3).
Expression difference(Expression minuend, Expression subtrahend)- returns anExpressionholding a difference between the given minuend and the given subtrahend. Consider following methods' implementation details:int evaluate()- returns the difference between the given minuend evaluation result and the given subtrahend evaluation result.String toExpressionString()- returns a string representation of the given difference. Example:product(val(1), val(2)).toExpressionString()results to(1 - 3).
Expression fraction(Expression dividend, Expression divisor)- returns anExpressionholding a ratio of the given dividend to the given divisor. Note that it refers to an integer division operation, i.e.fraction(val(3), val(4)).evaluate()result to0. Consider following methods' implementation details:int evaluate()- returns the ratio of the given dividend evaluation result to the given divisor evaluation result.String toExpressionString()- returns a string representation of the given fraction. Example:fraction(val(1), val(2)).toExpressionString()results to(1 / 2).
Important restriction: Note that in this exercise you may not add more non-anonymous classes.
Task
The purpose of this exercise is to train you to work with strings.
Estimated workload of this exercise is 60 min.
Please, implement StringUtil class methods:
Method signature:
public static int countEqualIgnoreCaseAndSpaces(String[] words, String sample)Return the number of words from words array that are equal to sample ignoring characters case and leading and trailing spaces.
If sample is null or words is null or empty, return 0. words is guaranteed to not contain null values.
Method signature:
public static String[] splitWords(String text)Split text string into array of words using following separating characters: ",", ".", ";", ":", " ", "?", "!".
For empty string, null string, and string consisting only of separating characters return null
Method signature:
public static String convertPath(String path, boolean toWin)Convert path to Unix\Windows path depending on a boolean parameter.
Unix path may start with ~ or /. Every subdirectory must end with / character except the last one.
Path elements . and .. refer to current directory and parent directory.
Filename doesn't necessarily have the extension.
Unix path examples:
/folder/../folder/file.txt/dev/nullfile.txtfolder/logs/~/user/some_logs
Windows path may start with C:. Every subdirectory must end with \ character except the last one.
Path elements . and .. refer to current directory and parent directory.
Filename doesn't necessarily have the extension.
Windows path examples:
file.txt\Program Files\some_file.exe.\to_do_list.txtC:\Users\..\Cygwin.\file
Let's consider Unix ~ path to correspond to Windows C:\User path and vice versa.
Let's consider Unix / root folder (i.e., when the path starts with /) to correspond to Windows C:\ drive and vice
versa (but C:\User still corresponds to ~).
If path already corresponds to the required format (for instance, is Windows path when Windows paths is needed and
toWin boolean parameter is true) return path.
If path is null, empty, or doesn't correspond to any path format (Unix, Windows), return null.
It is guaranteed that path is either a correct path, or it has some of the following errors:
- More than one
~ ~is not at the start~mixed with\(~in Windows path)- More than one
C: C:is not at the startC:mixed with/(C:in Unix path)\mixed with/
Illegal paths example:
/folder1/folder2\folder3C:\User/root/dev/~/C:/a/b/c/d~\folder~/~~~C:\Folder\Subfolder\C:\
Method signature:
public static String joinWords(String[] words)Join words from words array and return as a string in the following format: "[str_1, str_2, ..., str_n]".
If words is null or empty return null. words is guaranteed to not contain null values. words may contain empty strings, ignore them, i. e. don't put them in the resulting string. If words contains only empty strings return null.
- While implementing the methods you might need to come up with
regular expressions. You may consider using regex101.com to easier design of regular expressions. - You can and should use following methods\classes (click on the name):
You may use main method of StringUtil
class to test your implementation.
String[] words = new String[] {" nice ", "nICE", "nic3"};
String sample = "NICE";
int result = StringUtil.countEqualIgnoreCaseAndSpaces(words, sample); // 2
words = new String[]{" zoOm ", " z oom", " Z O O M "};
sample = "ZOOM";
result = StringUtil.countEqualIgnoreCaseAndSpaces(words, sample); // 1String text = " go with ...the:; FLOW ";
String[] result = StringUtil.splitWords(text); // ["go", "with", "the", "FLOW"]
text = ":..,,,::: ;;; ";
result = StringUtil.splitWords(text); // nullString winPath = "C:\\Program Files\\my_prog_file.py";
String unixPath = StringUtil.convertPath(winPath, false); // "/Program Files/my_prog_file.py"
unixPath = "../script.sh";
winPath = StringUtil.convertPath(unixPath, true); // "..\\script.sh"
unixPath = StringUtil.convertPath(unixPath, false); // "../script.sh"
unixPath = "//home/user/somefile";
winPath = StringUtil.convertPath(unixPath, true); // "C:\\home\\user\\somefile"String[] words = new String[]{"go", "with", "the", "", "FLOW"};
String result = StringUtil.joinWords(words); // "[go, with, the, FLOW]"Task
The purpose of this exercise is to train you to work with string values.
Estimated workload of this exercise is 45 min.
Please, implement validateColorCode method in ColorCodeValidation:
This method checks the input string for compliance with the rules for writing HTML Color Codes.
While implementing the methods you might need to come up with regular expressions. You may consider using regex101.com to ease designing them.
Note that input String may be null.
You can and should use following methods\classes:
-
Examples of valid hex codes:
#0B79E1 #6a8daf #002950 -
Examples of invalid hex codes:
123456 #afafah #-123
Task
The purpose of this exercise is to train you to work with string values.
Estimated workload of this exercise is 45 min.
Please, implement validateEpamEmail method
in EpamEmailValidation:
This method checks the input string for compliance with the rules for a regular EPAM email. Let us define them:
- A regular EPAM email includes firstname and lastname (in English), separated by underscore ("_").
- EPAM email always ends with "@epam.com"
- When a person gets new EPAM email, but email with this firstname and lastname is already registered, we add "1" to the new email. If such email is registered as well, we use "2" and so on.
While implementing the method you might need to come up with regular expressions. You may consider using regex101.com to ease designing them.
Note that input value may be null.
You can and should use following methods\classes:
-
Valid examples
william_shakespeare@epam.com lu_e@epam.com william_shakespeare1@epam.com william_shakespeare2@epam.com -
Invalid examples
william@epam.com william.shakespeare@epam.com william...shakespeare@epam.com william-shakespeare@epam.com shakespeare123@epam.com william_$hakespeare@epam.com
Task
The purpose of this exercise is to train you to work with exceptions, to raise them in particular.
Estimated workload of this exercise is 30 min.
Please, implement Requirements methods:
requireNonNull(Object)should throw new NullPointerException if object isnullrequireNonNull(Object, String)should throw new NullPointerException with message if object isnullcheckArgument(boolean)if boolean isfalseshould throw new IllegalArgumentExceptioncheckArgument(boolean, String)if boolean isfalseshould throw new IllegalArgumentException with messagecheckState(boolean)if boolean isfalseshould throw new IllegalStateExceptioncheckState(boolean, String)if boolean isfalseshould throw new IllegalStateException with messagecheckIndex(int, int)if index out of bounds throw new IndexOutOfBoundsException. Index must be inside[0, size)section.
Such methods might be helpful to check arguments, object states.
Task
The purpose of this exercise is to train you to work with exceptions, to handle them in particular.
Estimated workload of this exercise is 30 min.
Please, implement the main method in CatchEmAll class.
It must handle a call to a risky method that can throw different types of exceptions.
Please, note that some types of exceptions should be handled, while others – shouldn’t.
Details:
| What is thrown | How to handle |
|---|---|
| IOException | Wrap in an IllegalArgumentException with a message "Resource error" and throw it |
| FileNotFoundException | Wrap in an IllegalArgumentException with a message "Resource is missing" and throw it |
| ArithmeticException or NumberFormatException | Print a message of the thrown exception to System.err and do not throw anything |
| Any other Exceptions | Should not be caught |
Task
The purpose of this exercise is to train you to work with generics.
Estimated workload of this exercise is 30 min.
Please, use generics to change House class in order to dogs cannot enter cats' house and cats cannot enter dogs' house.
You need to alter residents field and enter methods of the House class.
Note that if you have done everything right, then two particular lines in the Main class may prevent successful compilation, so you may need to remove them.
See details in the Main class.
Task
The purpose of this exercise is to train you to work with enums.
Estimated workload of this exercise is 60 min.
Please, implement methods in Direction class:
ofDegrees- Return a Direction instance by input degrees ornullif there is none.closestToDegrees- Return the closest Direction instance to input degrees.opposite- Return a Direction instance that is opposite to this.differenceDegreesTo- Return the difference in degrees between this and input Direction instance.
Note that degrees input value may be out of the [0; 360) range. Adjust them accordingly.
Task
The purpose of this exercise is to train you to work with wrapper classes and their static methods.
Estimated workload of this exercise is 3 hours.
Please, implement methods in Battleship8x8 class.
Battleship8x8 represents a 8x8 map for Battleship game.
An important detail is that Battleship8x8 uses a ships field of long type to store ships locations
and a shots field of long type to register shots.
Fields of long type value store 64 bits each. Consider them as 8 rows per 8 cells. '0' bits represent empty cells, '1' bits represent cells seized by ships or registered shots.
public boolean shoot(String shot)- Registers a shot and returnstrueif the shot hits a ship. A shot is a combination of one of A-H letters and one of 1-8 digitspublic String state()- Returns a string representing state of the map. Map string is 8 lines per 8 characters separated by "\n". Use following symbols:- '.' - an empty cell
- '×' - an empty cell that has been shot
- '☐' - a cell seized by a ship
- '☒'- a cell seized by a ship that has been shot
You must not add or change new fields. Consider using static methods of wrapper classes.
Consider a map information encoded as a long value:
long map = -1150950973573693440L;You may consider it represented as binary literal:
/*
11110000
00000111
00000000
00110000
00000010
01000000
00000000
00000000
*/
long map = 0b11110000_00000111_00000000_00110000_00000010_01000000_00000000_00000000L;Consider rows be marked with digits and columns be marked with letters:
/*
ABCDEFGH
┌────────
1│11110000
2│00000111
3│00000000
4│00110000
5│00000010
6│01000000
7│00000000
8│00000000
*/Consider the following list of shots:
List<> shots = List.of("A1", "B2", "C3", "D4");Then we could use Battleship8x8 API:
Battleship8x8 battle = new Battleship8x8(map);
shots.forEach(battle::shoot);
System.out.println(battle.state());The result would be the following:
☒☐☐☐....
.×...☐☐☐
..×.....
..☐☒....
......☐.
.☐......
........
........
Task
The purpose of this exercise is to train you to work with arrays and optional.
Estimated workload of this exercise is 45 min.
Implement max method of MaxMethod class.
The correct implementation should receive an array of int values and return its maximum value.
Details:
- the method returns the result as OptionalInt
- if the input array is empty or
null, return empty OptionalInt.
int[] vals = new int[]{-2, 0, 10, 5};
OptionalInt result = MaxMethod.max(vals);
System.out.println(result.getAsInt() == 10); // trueTask
The purpose of this exercise is to prepare you to work with collections—to create and add elements and iterate through them to perform operations on each element.
Duration: 45 minutes
In this task, you will simulate the work of a new post office that takes parcels weighing between 0.5 and 20 kg and with a maximum volume of 0.25 m3
The Box class describes parcels. A parcel has the following characteristics: sender, recipient, weight, volume, and shipping cost. All characteristics except for the shipping cost are passed to the constructor to create an object. The shipping cost is calculated based on the weight, volume, and value of the parcel.
The NewPostOffice class has:
NewPostOffice()
Creates an office (an empty collection of parcels)Collection<Box> getListBox()
Returns a collection of parcels in the officestatic BigDecimal calculateCostOfBox(double weight, double volume, int value)
Calculates the cost of a parcel
Please proceed to the NewPostOffice class and implement its methods using an iterator:
Collection<Box> deliveryBoxToRecipient(String recipient)
Returns all parcels of a specified recipient; any parcels found must be removed from the officevoid declineCostOfBox(double percent)
Changes the cost of each parcel in the office by the percentage specifiedboolean addBox(String sender, String recipient, double weight, double volume, int value)
Creates a parcel, calculates its shipping cost, and adds it to the office
- The sender and receiver must exist.
- The weight must be 0.5–20.0 kg.
- The volume must be greater than 0 and less than 0.25 m3.
- The value must be greater than zero.
- The cost of a parcel is calculated as follows: the weight is multiplied by the cost of one kilogram, the volume is multiplied by the cost of one cubic meter, the value is multiplied by a given coefficient, then everything is summed up.
- If the values of the data above are set incorrectly (by specifying invalid values), the java.lang.IllegalArgumentException is thrown.
You may not use the Lambdas or the Streams API.
Task
The purpose of this exercise is to describe, create, and use lists that are built according to special rules.
Duration: 45 minutes
In this task, you will describe a list that is based on a dynamic array. The internal structure of the list is a one-dimensional array of the Object type with an initial capacity/size of 10 and a size field that stores the number of elements in the list. You must provide for the expansion of the array (list) capacity when the number of elements reaches 75% (load factor 0.75) of its size. Use the following expression to calculate the increase in capacity: Doub le the current capacity of the array and then multiply it by the load factor.
Now, please proceed to the SimpleArrayListImpl class, which implements the SimpleArrayList interface, and provide implementations of the following methods:
-
int size()
Returns the number of elements -
String toString()
Makes a string representation of the list -
boolean add(Object element)
Appends the specified element to the end of the list -
Object get(int index)
Returns an element at a specified position in the list -
Optional<Object> remove(Object element)
Searches for and removes the specified element -
int capacity()
Returns the current length of the list -
boolean decreaseCapacity()
Decreases the capacity of the list if it is 40% full or less
- The list is created by the default constructor, which creates an internal array with an initial length of 10 elements.
- The list cannot contain
nullelements. The add and remove methods must throw aNullPointerExceptionif they get null. - The get method must throw
IndexOutOfBoundsExceptionif the index is outside the [0 … size - 1] range. - The size field specifies the number of elements in the list and where to place the next element.
- The method for adding a new element must first check whether the capacity of the list should be increased before adding it.
- The
decreaseCapacity()method calculates the new capacity by doubling the current number of elements. - You can add any private methods to the
SimpleArrayListImpclass.
You may not:
- Use any type from the
java.utilpackage (or its subpackages) except for:java.util.Iteratorjava.util.Optional
- Add any additional fields into the
SingleArrayListImplclass. - Add any additional public methods to the
SingleArrayListImplclass.
Task
The purpose of this exercise is to create and use a custom doubly linked list.
Duration: 1 hour
In this task, you will describe a bidirectional list based on a linked representation. The internal structure of the list is a node chain (nested class Node) where each node encapsulates a list element and has one reference to the previous node and one reference to the following node. The first node has no reference to the previous node, and the last node has no reference to the next one.
Now, please proceed to the DoublyLinkedListImpl class, which implements the DoublyLinkedList interface, and provide implementations of the following methods:
-
boolean addFirst(Object element)
Inserts an element at the beginning of the list and returns true if an element is successfully added and, if not, false -
boolean addLast(Object element)
Appends an element to the end of this list and returns true if an element is successfully added and, if not, false -
boolean delete(int index)
Deletes an element by index and throwsIndexOutOfBoundsExceptionif the index is out of range -
Optional<Object> remove(Object element)
Returns and deletes the first occurrence of the specified element in the list -
boolean set(int index, Object element)
Finds the element at the specified index and replaces it or throws theIndexOutOfBoundsExceptionif the index is out of range -
int size()
Returns the number of elements in the list -
Object[] toArray()
Returns an array containing all the elements in order from first to last -
String toString()
Returns a string representation of the list
- The
DoublyLinkedListImplclass has two fields, head and tail, and should not contain a size field to store the number of elements. - The list is created by the default constructor, which initializes the head and tail fields to null.
- The list cannot contain null elements. The add, remove, and set methods must throw a
NullPointerExceptionif they get null. - The remove method must use the equals method to find the occurrence of the object in the list.
- The string representation of a list consists of all its elements separated by a space. For example, if a list contains three elements, o1, o2, and o3, the
toStringmethod returns "s1 s2 s3", wheres1=o1.toString(),s2=o2.toStribng(), ands3=o3.toString().
You may not:
- Use any type from the
java.utilpackage or its subpackages except forjava.util.Optional - Add additional fields to the
DoublyLinkedListImplandDoublyLinkedListImpl.Nodeclasses - Add any additional methods to the
DoublyLinkedListImpl.Nodeclass except constructors
Task
The purpose of this exercise is to work with List implementations, add/delete elements, and iterate over a collection to perform operations on each element.
Duration: 1 hour
In this task, you will simulate the work of the New Post Storage service, which accepts parcels (boxes) and prepares them for distribution to New Post offices.
The Box class describes a parcel with the following characteristics: sender, recipient, weight, volume, cost, city, and office. All characteristics are passed to the constructor to create an object. You must not change this class.
The NewPostOfficeStorage interface has several methods that perform add, delete, filter, and update operations in a storage:
boolean acceptBox(Box box)
Appends the specified parcel to the end of this storageboolean acceptAllBoxes(Collection<Box> boxes)
Appends to this storage all parcels that are contained in the specified collection. It must add either all the parcels or nothing, if an exception occursboolean carryOutBoxes(Collection<Box> boxes)
Removes from this storage all of its parcels that are contained in the specified collectionList<Box> carryOutBoxes(Predicate<Box> predicate)
Removes from this storage all of its parcels that are satisfied the specified predicateList<Box> getAllWeightLessThan(double weight)
Selects all parcels whose weight is less than the parameter value.List<Box> getAllCostGreaterThan(BigDecimal cost)
Selects all parcels whose cost is greater than the parameter value.List<Box> getAllVolumeGreaterOrEqual(double volume)
Selects all parcels whose volume is greater than or equal to the parameter valueList<Box> searchBoxes(Predicate<Box> predicate)
Searches parcels using a predicate. This method does not change the original storagevoid updateOfficeNumber(Predicate<Box> predicate, int newOfficeNumber)
Updates theofficefield in each box of this storage
Please, proceed to the NewPostOfficeStorageImpl
that the implementor of NewPostOfficeStorage interface.
Its highly recommended avoid indexed access to elements of a collection.
The Main class is not under tests. You can use it for your own purposes.
- Because the
Boxclass does not have any identity field the implementation must not check uniqueness ofBoxinstances. - Because the
NewPostOfficeStoragedescribes business logic not a collection, an implementation must not extend any existing implementation ofListinterface or implement it internally but must aggregate it instead. - You should choose the best existing implementation of the
java.util.Listinterface from the Java collection framework. - The implementation must not permit null values and must throw
NullPointerExceptionin such cases. - It is forbidden to use:
- lambda when you implement functional interfaces.
stream(),contains(),containsAll()indexOf()methods ofListinterface.for ( i )loop (use aforeachloop orIteratorwith awhile()loop or theforeach()method instead).
Task
The purpose of this exercise is for you to practice using collections, namely Set.
Duration: 45 minutes
In this task, you need to demonstrate how to work with a set of integers encapsulated in the RangedOpsIntegerSet class.
Please proceed to the RangedOpsIntegerSet class and provide implementations of the following methods:
-
boolean add(final Integer integer)
Adds a single value to the set -
boolean remove(final Object o)
Removes a single value from the set -
boolean add(int fromInclusive, int toExclusive)
Adds a range of values to the set (first argument—inclusive; last argument—exclusive); returns true if range values were actually added -
boolean remove(int fromInclusive, int toExclusive)
Removes a range of values from the list (first argument—inclusive; last argument—exclusive); returns true if range values were actually removed -
Iterator<Integer> iterator()
Returns an iterator to iterate over elements of the set in natural order -
int size()
Returns the number of current elements
You may not use lambdas or streams when implementing this task.
- Adding one range:
RangedOpsIntegerSet set = new RangedOpsIntegerSet();
set.add(1, 5);
for(Integer el : set){
System.out.println(el);
}Output:
1
2
3
4
- Adding two ranges:
RangedOpsIntegerSet set = new RangedOpsIntegerSet();
set.add(1, 5);
set.add(9, 11);
for(Integer el : set){
System.out.println(el);
}1
2
3
4
9
10
- Adding and removing ranges:
RangedOpsIntegerSet set = new RangedOpsIntegerSet();
set.add(1, 15);
set.remove(3, 12);
for(Integer el : set){
System.out.println(el);
}1
2
12
13
14
Task
The purpose of this exercise is to give you some practice using collections of the Set type.
Duration: 1 hour
In this task, you will determine the percentage of compliance of a certain team with project requirements. In other words, you will determine if the team is suitable for the project.
You have the following description:
- The
Positionenum defines a set of positions. - The
Skillenum defines a set of skills. - The
Levelenum defines a set of skill levels. - The
Memberclass defines a team member. Each member has a name, a level, and a set of skills (a collection of theSet<Skill>type implemented asEnumSet<Skill>). TThe team is described as a set of members in the form ofHashSet<Member>. - The
Roleclass defines the role of the participant in the project. Each role has a level, a position, and required skills (a collection of theSet<Skill>type implemented as anEnumSet<Skill>). - The
Projectclass defines the project and contains a description of it and a list of roles. - The
Project.Entryclass combines a skill and its level and is used in the algorithm for calculating the team's compliance with the project.
Now, please proceed to the Member class and implement its contents:
public Member(String name, Level level, Skill... skills)
Creates a member with the specified name, level, and skillsGetters
Return values of the appropriate fields
Now, please proceed to the Role class and implement its contents:
public Role(Position position, Level level, Skill... skills)
Creates a role with the specified position, level, and skillsGetters
Return values of the appropriate fields
Now, please proceed to the Project class and implement its contents:
public Project(Role... roles)
Creates a project with the specified rolespublic List<Role> getRoles()
Returns a list of rolespublic int getConformity(Set<Member> team)
Returns the percentage of team compliance with the project requirementsprivate static class Entry {}
Describes an entry containing a level/skill pair
- The
Entrymust implement the equals andhashCodemethods. Two entries are considered equal if and only if they have the same skill and level. - • To calculate the percentage of team compliance with project requirements, you must use the following algorithm:
- Generate a list of pairs
<Level, Skill>for the project's roles (e.g., named projectEntries). - Save the size of this list to a variable (e.g., originalSize).
- Generate a list of pairs
<Level, Skill>for the team members (e.g., named teamEntries). - Remove common elements from both lists.
- Calculate the compliance percentage as follows:
- Subtract the current size of the list of entries for the project roles from the originalSize variable
- Multiply the difference by 100
- Divide by the original size of the list of entries for the project roles
- Generate a list of pairs
You may not:
• Add extra fields to classes
• Add extra methods to classes
• Use lambdas or streams when implementing this task
- Suppose the project has the following roles:
• DEVELOPER which has the A1 level and the JAVA, DATABASE skills
• KEY_DEVELOPER which has the A3 level and the JAVA, DATABASE, SPRING skills
• TESTER which has the A2 level and the JAVA, SPRING, TESTING_TOOLS skills
Then the list of pairs will be:
projectEntries → [<A1, JAVA>, <A1, DATABASE>, <A3, JAVA>, <A3, DATABASE>, <A3, SPRING>, <A2, JAVA>, <A2, SPRING>, <A2, TESTING_TOOLS>]
And the list size is 8.
- Suppose the team has the following members:
• Member1 which has the A1 level and the JAVA, SPRING skills
• Member2 which has the A2 and the JAVA, DATABASE, SPRING skills
Then the list of pairs will be:
teamEntries → [<A1, JAVA>, <A1, SPRING>, <A2, JAVA>, <A2, DATABASE>, <A2, SPRING>]
- Removing the common elements in both lists yields the following result:
projectEntries → [<A1, DATABASE>, <A3, JAVA>, <A3, DATABASE>, <A3, SPRING>, <A2, TESTING_TOOLS>]
teamEntries → [<A1, SPRING>, <A2, DATABASE>]
The new size of the projectEntries list is 5.
- The compliance percentage is 37.5%.
Task
The purpose of this exercise is to learn how to use Map collections.
Duration: 1 hour 30 minutes
In this task, you will simulate work with a book catalog. The catalog can be represented as the TreeMap collection, where the author is the key and the list of published books is the value. You have the following description:
- The
Authorclass, which consists of the first and last name - The
Bookclass, which consists of the title, genre, and cost
Since the book catalog is an ordered map, the Author and Book classes must implement the Comparable interface.
The BooksCatalog class must have two constructors: a default one and one with a parameter that creates a map based on an existing map.
Please proceed to the Author and Book classes and provide implementations of the compareTo() method.
Please, proceed to the BooksCatalog class and provide implementations of the following methods:
List<Book> findByAuthor(Author author)
Returns a list of books by the specified author ornullif there is no such author in the catalogList<Author> findAuthorsByBook(Book book)
Returns a list of the authors of the specified book ornullif there is no such book in the catalogString getAllAuthors()
Returns a list of all the authors as a StringSet<Book> findBooksByGenre(String pattern)
Returns a set of books of the specified genre ornullif there are no books of this genreMap<Book, List<Author>> findAuthorsByBookTitle(String pattern)
Returns the book/author pair map. The search is carried out based on the words in the book's title
- To order the map by author, apply alphabetical order by first name and, if the names match, alphabetical order by last name.
- To order the map by book title, apply alphabetical order by title and, if the titles match, by ascending cost.
- The
findAuthorsByBookTitlemethod searches for books based on a word pattern; it is case-insensitive. - The
findBooksByGenremethod searches for books of a certain genre specified as a search pattern; the matching pattern and name of the genre are case-insensitive; all the books found are sorted using natural ordering. - You can use a regular expression to match occurrences of a pattern in a book title or genre in the
findBooksByGenreandfindAuthorsByBookTitlemethods. - The
getAllAuthorsmethod returns an alphabetical list of authors as a String, where the authors' names are separated by '\n'. - No methods of the
BooksCatalogclass acceptnull, and they must throw aNullPointerExceptionif they do. - You can use the
getData()method in the Util class to create the initial map. - You can add any private methods to the
BooksCatalogclass.
You may not use lambdas or streams when implementing this task.
Task
The purpose of this exercise is to work with Comparator implementations on the TreeMap maps.
Duration: 1 hour
In this task, you will simulate the work of the student's gradebook. The internal structure of the gradebook is a collection of the TreeMap type where a key is an object of the Student type, the value is a HashMap whose key is the name of a discipline (an object of the String type), and the value is the grade (an object of the BigDecimal type).
The Student class describes a student with the following characteristics: first/last name and group. All characteristics are passed to the constructor to create an object.
You must not change this class.
Now, please proceed to the StudentsGradebookImpl class, which implements the StudentsGradebook interface, and provide implementations of the following methods:
public GradeBookImpl()
Creates the gradebook object in which aComparatoris described to compare studentsboolean addEntryOfStudent(Student student, String discipline, BigDecimal grade)
Adds a student entry to the gradebook; returns true if the addition was successful, and false if not.int size()
Returns the number of students in the gradebookComparator<Student> getComparator()
Returns theComparator, which is used to compare studentsList<String> getStudentsByDiscipline(String discipline)
Gets a list of strings with students' names and their grades for the specified disciplines in the format"first_last name : grade"Map<Student, Map<String, BigDecimal>> removeStudentsByGrade(BigDecimal grade)
Finds, removes, and returns from the gradebook students who have a grade below the specified one in any discipline
If no such students are found, an empty map will be returnedMap<BigDecimal, List<Student>> getAndSortAllStudents()
Gets the gradebook as an ordered map where the key is the average grade and the value is a list of theStudenttype
- Since the
Studentobjects are the keys to the gradebook, when you create the gradebook, you will need to declare theComparatorto compare objects of theStudenttype and pass it to theTreeMap<Student, Map<String, BigDecimal>>constructor. - The grading scale for any discipline is in the range
[0 .. 5]. The minimum passing grade is3points. - The
removeStudentsByGrademethod returns a map ordered by theStudenttype. To create the resulting map, you must use theComparatorapplied in the gradebook constructor. - The
getAndSortAllStudentsmethod generates a gradebook based on the student's average grade. The average grade is indicated in increments of one tenth—for example, 3.1, 3.2, 3.3, etc. - It is guaranteed that the parameters passed to all methods are correct.
- You can add any private methods to the
StudentsGradebookImplclass.
You may not use lambdas or streams to complete this task.
Task
The purpose of this exercise is to apply various algorithms to collections using the methods of the Collections class.
Duration: 1 hour
In this task, you will simulate the work of a weekly maternity hospital journal. The internal structure of the journal is a collection of the Map type, where the key is the weekday (an enum of the WeekDay type) and the value is a list of babies born during the week (objects of the Baby type).
The Baby class describes a baby with the following characteristics: name, weight, height, gender, and birth time. All characteristics are passed to the constructor to create an object. You must not change this class.
Please note that once a birth journal has been created and filled in, it cannot be changed. This needs to be guaranteed.
Now, please proceed to the BirthJournalManagementImpl class, which implements the BirthJournalManagement interface, and provide implementations of the following methods:
boolean addEntryOfBaby(WeekDay day, Baby baby)
Adds an entry for the specified baby to the journal; returns true if the addition was successful and false if notvoid commit()
Makes the journal immutableint amountBabies()
Returns the number of babies born in a given weekList<Baby> findBabyWithHighestWeight(String gender)
Finds the baby of the specified gender with the highest weight
If there are multiple babies, it sorts them alphabetically by name.List<Baby> findBabyWithSmallestHeight(String gender)
Finds the baby of the specified gender with the smallest height
If there are multiple babies, it sorts them in order of increasing weightSet<Baby> findBabiesByBirthTime(String from, String to)
Finds babies born in the specified time period
- Time of birth is given as a
Stringin the form"hour:minute". - For implementations of all methods, the parameters passed to them are guaranteed to be correct.
- You can add any private methods to the
BirthJournalManagementImplclass.
You may not use lambdas or streams to complete this task.
Task
The purpose of this task is to practice with reading, processing and writing to a file using Java *Reader/*Writer
classes and their buffered variants, and using try-with-resources.
Duration: 1.5 hours
In this task you will implement LicenseReader#collectLicenses(File, File) method. It must read all license files
from root, format these licenses to a specific format and write all of them into outputFile.
root might be a directory or just a regular file. Please note that you need to collect files not only from the
root directory, but also from its subdirectories and their subdirectories, etc. All non-license files must be ignored.
Be aware, that this method must not throw any checked exception.
Take a look at the license header format:
---
License: <license name>
Issued by: <issuer>
Issued on: <date>
Expires on: <date>
---
The order of these properties is not restricted, so you may expect that Expires on might occur earlier than
License. All of them are mandatory except for Expires on. The date format is ISO date (yyyy-mm-dd). The license
is wrapped between lines containing 3 dashes (---). The file always starts with license header, otherwise it's just
a regular file.
If license header is invalid, then IllegalArgumentException must be thrown. If either root or outputFile is null,
then IllegalArgumentException must be thrown. If root does not exist, or it's not readable, then the same
exception must be thrown. And if root is a directory, but is not executable (means that it could not be entered),
then IllegalArgumentException must be thrown.
The output format for just one license looks like:
License for <file name> is <license name> issued by <issuer> [<issuedOn date> - <expiresOn date>]
Each line must contain the information about license in this format. If license does not have an expiration date,
then instead of <expiresOn date> - unlimited must be used.
If outputFile exists, then it must be cleared. So no appending is allowed.
collectLicensesmethod must verify thatrootis:- not null
- exists
- readable
- if it's a directory, then that it's executable
collectLicensesmethod must verify thatoutputFileis not null- if
outputFileis not empty, then it must be cleared before writing to it - all files and directories of
rootmust be processed - non-license files must be ignored
- license files must be processed and info about it must be stored in
outputFile(see formats inDescriptionsection) - if license format is invalid, or any verification is failed, then
IllegalArgumentExceptionmust be thrown - all license properties are mandatory, except for
Expires on(it's optional) - the order of license properties are undefined
- the order in the resulting file does not matter
- if
Expires onis omitted, then inunlimitedmust be used collectLicensesdoes not throw any checked exceptionBufferedWriter/BufferedReadermust be used for IO operations- All IO buffered streams must be defined using
try-with-resourcessyntax
libA/libraryA.lic
---
License: GNU
Issued by: GNU Commitet
Issued on: 2020-01-01
Expires on: 2025-01-01
---
Library description...
libraryB.lic
---
License: Custom
Issued by: Goverment
Issued on: 1984-04-13
---
Top secret info...
output
License for libA/libraryA.lic is GNU issued by GNU Commitet [2020-01-01 - 2025-01-01]
License for libraryB.lic is Custom issued by Goverment [1984-04-13 - unlimited]
Task
The purpose of this exercise is to give you some practice managing I/O streams.
It should take you about 30 minutes to complete this task.
You will implement an input stream to process data from the file. Please also implement a util class to check a file and return a ciphered text.
Please implement methods in the CipherCreator class.
public static StringBuilder cipherText(File input)- takes a file as an input and returns a ciphered text.
Please override methods in the TransformerInputStream class.
public int read()- reads the next data byte and returns a ciphered byte.public void close()- closes the stream and prints a message about it to the console.
Cipher key points:
- The text can only contain letters, and each word is written on a new line.
- Each letter of the ciphered text is shifted by two characters from the original one, case-sensitive. A -> C, f ->h.
- The alphabet is looped. It means Z -> B, y -> a.
- All other characters are ignored.
Test
cipher
For
Fundamentals
Of
Programming
XYZ
zyx
CamelCase
DiScO
cipherText(file);
// Vguv
// ekrjgt
// Hqt
// Hwpfcogpvcnu
// Qh
// Rtqitcookpi
// ZAB
// baz
// EcognEcug
// FkUeQ "Hi"
10101
!--!
cipherText(file);
// Jk
//
//Task
The purpose of this exercise is to practice the usage of Java Scanner and Formatter classes.
Estimated workload of this exercise is 60 minutes.
The Car class represents a car with some attributes:
- brand
- model
- cylinder capacity
- performance
- acceleration
The first part of the exercise is to read cars from a CSV (comma-separated values) file. The CSV file contains the car attributes in the same order as listed above.
Implement the CarCsvReader class's readCars(File file) method to do the job.
- Read the file content line-by-line with
BufferedReader. Then create aScannerand configure it to use comma (,) as delimiter.
Input file example:
Toyota,Corolla,1599,75,6.8
Kia,Rio,1225,68,10.3
Once the cars are in memory, print them to the console in the following way
- brand: 10 characters width
- model: 10 characters width
- cylinder capacity: 5 digits, add measurement unit: ccm
- performance: 3 digits, add measurement unit: kw
- acceleration: 5 digits, add measurement unit: sec
Implement the FormattedCarPrinter class's print(List<Car> cars) method.
Output example, given the above list of cars:
Toyota Corolla 1599 ccm 75 kw 6.80 sec
Kia Rio 1250 ccm 68 kw 10.30 sec
The Application class is already implemented, which delegates
the reading task to CarCsvReader class, and the formatting task to FormattedCarPrinter class.
The starter project includes a sample cars.csv file in data directory. The application has to read that file.
Task
The purpose of this exercise is to train you to manage files and directories using Java NIO.
Duration: 1.5 hour
You must implement a method to build a directory representation. You can also create other methods for convenience that will be called from the 'tree' method.
Please implement methods in the FileTree class.
public Optional<String> tree(final Path path)- takes a path to a file/directory as an input parameter and builds a String representation of its hierarchy.
-
If a given path does not exist, return an empty Optional.
-
If a given path refers to a file, return a String with its name and size like this:
some-file.txt 128 bytes -
If a given path refers to a directory, return a String with its name, total size and full hierarchy:
`
some-dir 100 bytes
├─ some-inner-dir 50 bytes
│ ├─ some-file.txt 20 bytes
│ └─ some-other-file.txt 30 bytes
└─ some-one-more-file.txt 50 bytes
`
- Use pseudo-graphic characters to format the output.
- Compute the size of a directory as a sum of all its contents.
- Sort the contents in the following way:
- Directories should go first.
- Directories and files are sorted in lexicographic order (case-insensitive).
Task
The purpose of this exercise is to familiarize you with the mechanism of complex object serialization/deserialization.
Duration: 1 hour
In this exercise, you need to implement the serialization of complex objects of the Order type. Below is a hierarchy of classes that describe orders.
The Order class represents an order:
id
A unique identifier of the ordertotal
The cost of the order, which is automatically calculated and can only be readitems
A map that stores products (a ke y is an object of theItemtype) and the number of units to be purchased (a value is a variable of theinttype)
The Item class represents a product:
id
A unique identifier of the productname
The name of the productdescription
A short description of the productcharacteristics
A list of product features (objects of theItemCharacteristictype)
The abstract class ItemCharacteristic represents one characteristic of a product and is the supertype for different types of product characteristics:
id
A unique identifier of the characteristicname
The name of the characteristictype
A data type of the characteristic (It can beString,Integer,Double, etc.)
The IntItemCharacteristic class represents an integer characteristic and inherits the ItemCharacteristic class:
value
Keeps a value of the characteristic
The DoubleItemCharacteristic class represents a numeric characteristic and inherits the ItemCharacteristic class:
value
Keeps a value of the characteristic
The OrderSerializer class serializes and deserializes objects of the Order class:
public static void serializeOrder(Order order, OutputStream out) throws IOException
Serializes a specified object of the Order class into the given data output streampublic static Order deserializeOrder(InputStream in) throws IOException, ClassNotFoundException
Deserializes a specified object of theOrderclass from the given data input stream
-
• Each entity class must contain a constructor that accepts values for all fields and can contain any other constructors if necessary.
-
• All entity classes must have getters and setters for all fields.
-
• All entity classes must contain an overridden
equals()method by all fields. -
• The
ItemCharacteristicclass must beabstractand must not implement theSerializableinterface. -
• When calculating the cost of an order in the
Orderclass, set thetotalfield value using the following algorithm:- If the
totalfield isnulland theitemsfield is notnull, then a call of thegetTotal()method must calculate thetotalvalue. - If the
itemsfield isnull, thetotalmust be zero. - It is guaranteed that the internal state of the
itemsfield will not change after being installed in the object.
- If the
-
• The custom serialization mechanism must be implemented in all descendants of the
ItemCharacteristicclass because it is not serializable.
- You may not use the serialization mechanism with the
Externalizableinterface.
Task
The purpose of this task is to train you to declare your functional interface, practice a little more with generics, and see an example of why you might want to declare your interface when we have plenty of predefined ones.
Duration: 15 minutes
In this task, you'll implement the so-called ThrowingFunction.
It's a variant of a java.util.function.Function, except for it may throw
an exception. It might be really helpful when you want to pass a function
to some method, but the underlying code throws some checked exception
(it happens pretty often, when you work with Java IO, for example).
But what exception it might throw? IOException, or ClassNotFoundException,
or just Exception, or even Throwable? Well, let's try to use generics here.
We want to declare a function that would throw an exception, which we can specify.
There is also a pretty common practice to define "companion" methods for such
functions. Usually, they called something like silent, wrap, quiet, etc.
The main idea of such companions is to wrap the throwing function and return
the non-throwing function. It's useful when you need to pass your throwing function
to some API that accepts only non-throwing ones (e.g. Stream API).
Let's go through the requirements of this task:
ThrowingFunctioninterface must be declared underedu.epam.fop.lambdaspackage- It must be a generic type with generalized:
- Argument type
- Return type
- Exception type
- It must have an abstract
applymethod, which accepts one argument, of one generic type and returns an instance of another generic type applymethod must be able to throw any exception up toThrowable- It must have a static method for wrapping
ThrowingFunctionintoFunction, namedquiet quietmethod must be generic tooquietmethod must returnnullwhennullis passedquietmethod must not throw any exception- The returned by
quietmethodFunctionmust wrap any occurred inThrowingFunctionexception intoRuntimeExceptionwithout hiding the cause - The returned by
quietmethodFunctionmust work just asThrowingFunction, when no error has occurred - generic types of
ThrowingFunctionandFunctionmust correspond to each other - Generic types must not have any boundaries if possible
ThrowingFunctionmust be annotated with@FunctionalInterface
ThrowingFunction<String, Integer, IOException> ioFunc = new ThrowingFunction<>() {
@Override
Integer apply(String fileName) throws IOException {
return IOUtils.getSize(fileName);
}
}try {
return ioFunc.apply("big-file.csv");
}
catch (IOException e) {
e.printStackTrace();
}Function<String, Integer> func = ThrowingFunction.quiet(ioFunc);
func.apply("big-file.csv");Task
The purpose of this task is to practice writing simple and concise Java lambda expressions.
Duration: 30 minutes
Your task is to provide a Java lambda expression that implements DoubleFunction<String>.
As the name of the functional interface indicates it accepts a double value,
which we want to format to the corresponding String value in the format:
[-]\d+[.\d] %
Where [...] means optional, \d means digit, and + means at least one symbol.
Please note, the space between the number and percent sign. This lambda must never return null.
The passed value can be anything, even more than 1 or less than 0. The value 1 we consider 100 %, so -0.5 would be -50 %.
- Convert the
doublevalue to the correspondingStringvalue, representing the double value as a percent string. - Never return
null. - A
-sign before the number in a string of negative values. - A space between the resulting number and the percent sign.
- A maximum of one digit in the fraction part.
- You must round the fraction part mathematically, i.e. anything less than 0.5 is rounded down (floor),
and anything greater than or equal to 0.5 is rounded up (ceil). For example:
- 1.4 => 1
- 2.45 => 2
- 3.5 => 4
- 17.7000001 => 18
- (Optional) Make the lambda one line (i.e., without using curly brackets)
The lambda can be tested using the following call, which returns a String value for testing:
PercentageFormatter.INSTANCE.apply(<double value>);And here are some expected input/output pairs:
- 0.42 =>
42 % - 0.427 =>
42.7 % - 0.4273 =>
42.7 % - 0.4275 =>
42.8 % - -0.4275 =>
-42.8 %
Task
The purpose of this task is to practice with Optional, and its main methods - map, filter, flatMap, etc.
Duration: 3 hours
In this task, you are provided with some classes that are used for insurance calculations.
In the insurance package you have:
Subject- the main sealed interface, which must be implemented by insurance subjects.Car,Accommodation,Person- the subject's insurance is calculated for (which implement theSubjectinterface).Currency- just anenumof the currencies provided.RepeatablePayment- represent, for example, rent, salary, or a loan.Injury,Family- not subject classes; used to describe a certain part of the subject classes.
These classes a mostly plain data objects without any logic. The only things to highlight are:
- Some getters return
Optionalinstead of the target type. - Some of these classes implement
Comparableinterface to make it easier to retrieve the required instance fromSortedSet.
Also, you have calculator package. Here you have two main classes:
InsuranceCoefficient- a wrapper forintvalue in range [0; 100], which represents the percentage of trustworthy clients.InsuranceCalculator<S extends Subject>- a functional interface, which determinesInsuranceCoefficientbased on the passedSinstance.
Also, here you can find several *InsurancePolicies classes, which provide methods that must be implemented.
Take a closer look at them and define the requirements.
No implementations must throw an exception, and all of them must be null-safe. Objects can be null or return null.
Getters that return Optional never return null.
All arguments cannot be null.
Accepts BigInteger divider which is used to adjust the insurance coefficient.
It must return an insurance coefficient when an accommodation is rented; monthly payment should be in USD.
As a result, for the insurance coefficient, you must divide the rent amount by the divider provided.
If the resulting insurance coefficient is more than 100, then InsuranceCoefficient.MAX is returned.
If a condition is not met, then return empty Optional.
- The accommodation must include
rent. - The rent period must be in months.
- The rent currency must be USD.
- The rent amount must be greater than 0.
- The coefficient is equal to rent divided by the divider provided in percent (
rent / divider * 100%). - If the relation is more than 100%, 100% should be returned.
- The default value is
Optional.empty
Accepts BigInteger priceThreshold, which must be met or exceeded by the accommodation price,
int roomsThreshold, which must be met or exceeded by the room counts,
and areaThreshold are the same but for the accommodation area.
Accommodations price, room count, and the area must be greater or equal to their corresponding thresholds.
If all the conditions are met, InsuranceCoefficient.MAX must be returned;
if not InsuranceCoefficient.MIN must be returned.
- Accommodation price >=
priceThreshold - Accommodation rooms >=
roomsThreshold - Accommodation area >=
areaThreshold - Return
InsuranceCoefficient.MAXif all conditions are met - Return
InsuranceCoefficient.MINif one or more conditions are not met
Accepts LocalDate baseDate, which is used as a pivot point for calculations. All calculations must use it.
Date-math precision is 1 day.
The calculator must return:
InsuranceCoefficient.MAXif the manufactured date is less than 1 year frombaseDate- A coefficient of 70 if less than 5 years
- A coefficient of 30 if less than 10 years
InsuranceCoefficient.MINif a car is older than 10 years.- If the manufactured date is unknown,
Optional.emptymust be returned
Accepts LocalDate baseDate as a base for the date-math calculations,
BigInteger priceThreshold which must be met or exceeded by car price,
and Period owningThreshold - the minimum period of ownership.
The idea is to calculate the insurance coefficient only for cars which are still owned by a person (soldDate is not set),
price is greater or equal to priceThreshold, the period from purchaseDate to baseDate
is greater or equal to owningThreshold.
The resulting coefficient must be based on car price and priceThreshold.
If the price of the car is greater than or equal to three times the priceThreshold,
InsuranceCoefficient.MAX must be returned. If it exceeds two times but is less than three times greater,
a coefficient of 50 must be returned. InsuranceCoefficient.MIN must be returned
if the price is less than or equal to twice the threshold.
If any of the conditions are not met, Optional.empty must be returned.
soldDatemust not be set.pricemust be >= thanpriceThreshold.purchaseDate+owningThresholdmust be >=baseDate.InsuranceCoefficient.MAXmust be returned ifprice>= 3 *priceThreshold.- A coefficient of 50 must be returned if 3 *
priceThreshold>price>= 2 *priceThreshold. InsuranceCoefficient.MINmust be returned ifprice< 2 *priceThreshold.Optional.emptymust be returned if any of the conditions are not met.
Accepts int childrenCountThreshold. The coefficient must be calculated based on the number of children
a person has relative to the threshold provided.
- A person must have a
family. - A person must have
children. - The resulting coefficient equals to
max(100, childrenCount / threshold). InsuranceCoefficient.MINmust return if any of the conditions are not met.
Accepts BigInteger salaryThreshold and Set<Currency> currencies,
which together define the salary threshold based on the amount and the currency allowed.
- Person must have an employment history of at least four records.
- They must have multi-currency account.
- They must not have any recorded injuries.
- They must have at least one accommodation (either owned or rented).
- They must be currently employed (i.e., the last employment record does not have
endDate). salaryfor this job must be in one of thecurrenciesprovided.salary.amountmust be greater than or equal tosalaryThreshold.- If all conditions are met, a coefficient of 50 must be returned.
- If any of the conditions are not met,
Optional.emptymust be returned.
Accepts Set<EmergencyStatus> statuses, which defines the allowed emergency statuses
of an accommodation owned or rented by a person.
- A person must have an accommodation.
- The calculator must pick the accommodation that is the smallest in area.
- Check to make sure its
emergencyStatusis listed in thestatusesparameter. - The coefficient is calculated as
100 * (1 - status.ordinal() / totalStatuses). - If any of the conditions are not met,
Optional.emptymust be returned.
Accepts BigInteger rentThreshold.
- A person must have an injury.
- The injury must have been caused by someone else.
- The largest accommodation (by area) must be rented.
- The rent must be in GBP.
- The coefficient is calculated as
max(100, 100 * rent / threshold). - If any of the conditions are not met,
Optional.emptymust be returned.
Task
The purpose of this exercise is to train you in usage of Java Stream API in basic level.
Estimated workload of this exercise is 30 minutes.
MovieQueries class is responsible to perform different queries on a list of movie titles.
Please implement MovieQueries constructor and methods according to the following method definitions.
Please do not change method names, arguments, or return type of the methods:
| Method name | Description |
|---|---|
getNumberOfMovies |
Count the elements in the movie list. |
getNumberOfMoviesThatStartsWith |
Count the elements that start with given parameter. |
getNumberOfMoviesThatStartsWithAndEndsWith |
Count the elements that start and end with the given parameters. |
getLengthOfTitleOfMovies |
Count the length of all movie titles. |
getNumberOfLettersInShortestTitle |
Return the length of the shortest movie title. Throw IllegalArgumentException if the list is empty. |
getFirstTitleThatContainsThreeWords |
Return the first movie title that contains three words. |
getFirstFourTitlesThatContainAtLeastTwoWords |
Return the first four (and only four) movie title that contains at least 2 words. |
printAllTitleToConsole |
Print all movie titles to the console. |
MovieQueries constructor must throw IllegalArgumentException if the parameter is null.
In this exercise use Stream API, do not implement for loop, while loop or any other imperative approach.
Having the following test data:
"Terminator", "Blade Runner", "Star Wars", "Indiana Jones", "Friends",
"The Magnificent Seven", "The Dark Knight", "The Lord of the Rings: The Return of the King",
"Pulp Fiction"
getNumberOfMoviesThatStartsWithcalled with parameter"The", returns 3.getFirstTitleThatContainsThreeWordsreturns"The Magnificent Seven"
The Application class is already implemented, which delegates
the querying task to MovieQueries class.
Task
The purpose of this exercise is to practice Java Stream API at intermediate level. The data model is similar to the previous exercise, movie. In this exercise the model is based on movies, but more complex.
Estimated workload of this exercise is 90 minutes.
The stream operations are defined on movie data. There are two domain model classes: Movie and Person.
Person can be the director, writer or cast of the movie..
Person example:
name: Arnold Schwarzenegger
date of birth: July 30, 1947
biography: With an almost unpronounceable surname and a thick Austrian accent
Movie example:
title: The Terminator
description: A human soldier is sent from 2029 to 1984 to stop an almost indestructible cyborg killing machine.
genres: ACTION, SCI_FI
length: 107 (minutes)
release year: 1984
directors: James Cameron
writers: James Cameron, Gale Anne Hurd, William Wisher
casts: Arnold Schwarzenegger, Linda Hamilton, Michael Biehn
Note: directors, writers and casts fields are collections that hold Person reference.
MovieQueries class is responsible to perform different queries on a list of movies.
Please implement MovieQueries constructor and methods according to the following method definitions.
Please do not change method names, arguments, or return type of the methods:
| Method name | Description |
|---|---|
checkGenreOfAllMovies |
Check that all the movies in the list belongs to the given genre. |
checkGenreOfAnyMovies |
Check that at least one movie in the list belongs to the given genre. |
checkMovieIsDirectedBy |
Check that at least one movie in the list is directed by the given person. |
calculateTotalLength |
Calculate the total length of all the movies in the list. |
moviesLongerThan |
Count the movies that are longer then the given parameter. |
listOfWriters |
Return the writers of all movies. One writer appear only once in the list. |
movieTitlesWrittenBy |
Return the titles of movies that are written by the given person. |
listOfLength |
Return a list of the length of movies. |
longestMovie |
Find the longest movie. Throws IllegalArgumentException if the movies list is empty. |
oldestMovie |
Find the oldest movie. Throws IllegalArgumentException if the movies list is empty. |
sortedListOfMoviesBasedOnReleaseYear |
Return a sorted list of movies based on their release year. |
sortedListOfMoviesBasedOnTheDateOfBirthOfOldestDirectorsOfMovies |
Return a sorted list of movies based on the date of birth of the oldest director of each movie. |
moviesReleasedEarlierThan |
Return a list of all the movies which are released earlier than the given year (inclusively). |
MovieQueries constructor must throw IllegalArgumentException if the passed parameter is null.
In MovieQueries implementation you can expect that the Movie and related Person objects passed as arguments are all valid,
each field is populated with non-null values. No need to validate them.
Use only Java Stream API.
Having the following movies:
The Terminator
genres: ACTION, SCI_FI
Blade Runner
genres: ACTION, SCI_FI, DRAMA
Indiana Jones
genres: ACTION, ADVENTURE
checkGenreOfAllMovies(Genre.SCI_FI)returns falsecheckGenreOfAnyMovies(Genre.SCI_FI)returns true
The Application class is already implemented, which delegates the querying task to MovieQuery class.
You can find the models in model package.
MovieDataStore builds test data and provide them to the application.
Classes in builder package helps to create models.