Svitlana-Berezhna / java-homeworks

Java Homeworks (Java for Software Test Automation Engineers Course).

Homework № 1

LEARNING OF DATA TYPES AND OPERATIONS WITH THEM

Task № 1:

Write a Java program that:

• describes a three-digit integer number number (for example, 123);
• finds and displays to the console the difference between number number and number composed of the digits of the number, but taken in reverse order (for the specified example, the reverse number is 321).

Task № 2:

Write a Java program that converts the weight given in pounds to kilograms, but outputs the number of received kilograms and grams separately (in 1 lb 453.6 grams).

Task № 3:

Write a Java program that calculates and displays to the console the amount of profit for a given deposit (for example, 10000) for a given number of months (for example, 6) at a specified percentage per annum (for example, 12%).

Requirements:

1. Use variables to store program data.
2. Use arithmetic operations for calculations and, if necessary, data types casting.
3. Use the System.out.println(...) operator to output the result of calculations.
4. Read books:
   • Head First Java, O'Reilly.
   • Java Code Convention.
   • Clean Code, Robert C. Martin.
5. Watch the video https://itvdn.com/ru/specialities/java-developer.

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Homework № 2

LEARNING OF OPERATORS

Task № 1:

Write a Java program that fills in with asterisks (*) and displays to the console the triangles shown in the figure:

Requirements:

1. During the coding should be used Java coding conventions.
2. Keep reading books:
   • Head First Java, O'Reilly.
   • Java Code Convention.
   • Clean Code, Robert C. Martin.
3. Keep watching the video https://itvdn.com/ru/specialities/java-developer.

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Homework № 3

LEARNING OF METHODS AND PROCESSING LINE

Task № 1:

Write a Java program that inputs some string and prints to the console all the unique characters of this string. String processing is done in a separate method.

Task № 2:

Write a Java program that inputs an integer, converts it to binary representation, storing it as a string, and prints the result to the console. The conversion is done in a separate method.

Requirements:

1. During the coding should be used Java coding conventions.
2. Methods of data processing should not carry out the output of the result, it should be returned from methods.

Additional tasks for those who wish:

Task № 1:

Write a Java program that:

• inputs an integer variable and outputs the result of its processing;
• processing is a method that gets an integer, determines the last two digits and returns them as a string of characters in reverse order. For example, the number is 2546, the result is "64".

Task № 2:

Write a Java program that:

• inputs the height of the pyramid and passes it to the method for outputing the pyramid;
• the method outputs to the console the pyramid of the obtained height (value in the range from 1 to 9). For example, for height = 3:

1

121

12321

1234321

Task № 3:

Write a Java program that:

• describes a method that finds and returns the first character of the word under the given number in the given string. Restriction: words in a line are separated only by spaces.
• inputs some text and a word number, and then uses a method to process and outputs the result.

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Homework № 4

LEARNING OF ARRAYS

Task № 1 - Processing without branchings:

Write a Java program that creates an array of any type and then prints it to the console in forward and backward order.

Task № 2 - Creating a third array of known length:

Write a Java program that creates two arrays of the same dimension, and then creates a third one of the same dimension and fills it with the pairwise sum of elements from the first two ones.

Task № 3 - Creating a third array of unknown length:

Write a Java program that creates an array of any type, and then separates it into two ones: from positive and negative elements.

Requirements:

1. During the coding should be used Java coding conventions.
2. If possible, processing arrays to do in a separate method.
3. The dimension of the array can be set explicitly or entered by typing from the keyboard.
4. Fill the original arrays with random values (for example, use the Math.random() method).
5. For clarity of the completing the task, it is necessary to output the arrays before and after processing in cases where the original array changes.

Additional tasks for those who wish:

Task № 1

Write a Java program that creates an array of any type, and then calculates the arithmetic mean of the array elements and the number of array elements that are greater than this arithmetic mean.

Task № 2

Write a Java program that creates two arrays of different dimensions and then creates a third array as a concatenation of the two original ones.

Task № 3

Write a Java program that creates an array of any type and then determines the maximum and minimum values of the array elements and removes their duplicates.

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Homework № 5

LEARNING OF CLASSES

Task № 1:

Write a Java program in which:

• describe a well encapsulated Book class (ID, Title, Author, Publisher, Year of publication, Number of pages, Cost), i.e. private fields with accessor methods. Add a constructor to the class with all parameters. Add a view() method to the class to display (output) the object.
• describe the Books class, which will contain an array of objects (field) of the Book type; constructor that takes the size of an array and allocates memory for it; method of adding one book; method to display all books in an array; method of changing the cost of books by a specified number of percent; search method for all books of the specified author; search method for all books published after the specified year.
• describe a class with a main() method, in which you enter the dimension of an array of books and create an object of type Books; create and add objects of type Book to an object of type Books; display a set of books to the console; use all other methods of class Books.

Requirements:

1. During the coding should be used Java coding conventions.
2. Use the Scanner class to enter a percentage value from the keyboard to change the cost of books, author and year of publication for the selection of books.
3. Search methods should return a new object of type Books, which encapsulates an array of found books (if the array is empty, then provide the output of the corresponding message).

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Homework № 6

LEARNING OF OOP PRINCIPLES: INHERITANCE AND POLYMORPHISM

Task № 1:

Write a Java program in which:

• describe the Shape class(field color, constructor, overridden toString() method (a string like "class=...: color=..."), a method for calculating the area of a shape calcArea(), which returns a value of 0.0).
• describe the Circle class as a subclass of Shape. The Circle class contains: field radius, constructor, overridden toString() and calcArea() methods.
• describe the Rectangle class as a subclass of Shape. The Rectangle class contains: width and height fields, constructor, overridden toString() and calcArea() methods.
• describe the Triangle class as a subclass of Shape. The Triangle class contains: fields a, b, c; constructor, overridden toString() and calcArea() methods.
• describe the class Main with the main() method, in which create an array of shapes (four rectangles, three circles, two triangles) and display it to the console along with the area information of the shapes. Provide some method of the Main class to output the array of shapes.
• add a method to the Main class for calculating the total area of all shapes of the created array.
• add a method to the Main class for calculating the total area of a specific shape type in the created array.
• add the call of the described methods to the main() method.

Requirements:

1. During the coding should be used Java coding conventions.
2. Use the instanceof operator to determine the type of shape.

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Homework № 7

LEARNING OF INTERFACES AND EXCEPTIONS HANDLING

Task № 1:

Open the program created on Homework № 5 and make the following changes:

• replace the view() method with the toString() method in the description of the Book class and change the code that used the view() method to appropriate applying of toString() method.
• provide for handling incorrect data input by user through the exception handling mechanism (to do this, describe your exceptions). For example, you describe the Validator class, which contains methods for checking of something for something, and use its methods to validate the entered values. If all is well, the program continues to work, but if the data is not correct, you throw an exception, and the code using validation should handle the exception.
• supplement the Books class with methods of sorting the set of books by author alphabetically, by publisher in alphabetical order, by cost in descending order. Consider when sorting that the original set should not change, this only changes its presentation to the user, i.e. you need to apply copying an array of books before sorting.

Requirements:

1. During the coding should be used Java coding conventions.
2. Use the Comparator interface to describe the rule for comparing books by the specified criterion.