Practice Constructors

Topics

1. Implementing Constructors
2. Updating Previous Exercises with Constructors
3. Next Topic: Methods

Implementing Constructors: New Exercises to Practice Writing Constructors

Here are a few new exercises to help you practice writing constructors in Java. Each exercise involves creating a class with fields and adding constructors to initialize those fields.

Exercise 1: Library Class

Scenario: Create a class to represent a library.

• Class Name: Library
• Fields:
  • String libraryName – The name of the library.
  • String address – The address of the library.
  • int numberOfBooks – The number of books available in the library.

Tasks:

1. Default Constructor: Write a constructor that initializes the library with a default name, address, and number of books.
2. Parameterized Constructor: Write a constructor that takes libraryName, address, and numberOfBooks as parameters to initialize the fields.

Instructions for Testing:

• Create a LibraryTester class.
• In the main method, create instances of Library using both the default and parameterized constructors.
• Print out the field values to verify that the constructors work as expected.

Exercise 2: MovieTicket Class

Scenario: Create a class to represent a movie ticket.

• Class Name: MovieTicket
• Fields:
  • String movieName – The name of the movie.
  • String seatNumber – The seat number for the ticket.
  • double price – The price of the ticket.

Tasks:

1. Default Constructor: Write a constructor that sets default values for movieName, seatNumber, and price.
2. Parameterized Constructor: Write a constructor that takes movieName, seatNumber, and price as parameters to initialize the fields.

Instructions for Testing:

• Create a MovieTicketTester class.
• In the main method, create instances of MovieTicket using both the default and parameterized constructors.
• Print out the field values to ensure they are correctly set by the constructors.

Exercise 3: Smartphone Class

Scenario: Create a class to represent a smartphone.

• Class Name: Smartphone
• Fields:
  • String brand – The brand of the smartphone.
  • String model – The model of the smartphone.
  • double price – The price of the smartphone.

Tasks:

1. Default Constructor: Write a constructor that assigns default values to brand, model, and price.
2. Parameterized Constructor: Write a constructor that initializes brand, model, and price with provided values.

Instructions for Testing:

• Create a SmartphoneTester class.
• In the main method, create instances of Smartphone using both the default and parameterized constructors.
• Print out the field values to check if the constructors are working as expected.

Exercise 4: Course Class

Scenario: Create a class to represent a course in a school or university.

• Class Name: Course
• Fields:
  • String courseName – The name of the course.
  • String courseCode – The code for the course.
  • int credits – The number of credits the course is worth.

Tasks:

1. Default Constructor: Write a constructor that sets default values for courseName, courseCode, and credits.
2. Parameterized Constructor: Write a constructor that accepts courseName, courseCode, and credits as parameters to initialize the fields.

Instructions for Testing:

• Create a CourseTester class.
• In the main method, create instances of Course using both the default and parameterized constructors.
• Print out the field values to verify the constructors are working properly.

Exercise 5: WeatherReport Class

Scenario: Create a class to represent a weather report.

• Class Name: WeatherReport
• Fields:
  • String location – The location of the weather report.
  • double temperature – The temperature at that location.
  • String condition – The weather condition (e.g., sunny, rainy).

Tasks:

1. Default Constructor: Write a constructor that initializes the fields with default values.
2. Parameterized Constructor: Write a constructor that takes location, temperature, and condition as parameters to initialize the fields.

Instructions for Testing:

• Create a WeatherReportTester class.
• In the main method, create instances of WeatherReport using both the default and parameterized constructors.
• Print out the field values to ensure that the constructors are setting the fields correctly.

Updating Previous Exercises with Constructors

Now, let’s update the classes from the previous exercises by adding constructors.

1. Student Class

• Add:
  • A default constructor that sets default values for studentId, name, and gpa.
  • A parameterized constructor that takes studentId, name, and gpa as arguments.
• Instructions for Testing:
  • In the StudentTester class, create instances using both constructors and print the field values to verify the updates.

2. Book Class

• Add:
  • A default constructor that initializes isbn, title, and author with default values.
  • A parameterized constructor that accepts isbn, title, and author as arguments.
• Instructions for Testing:
  • In the BookTester class, create instances using both constructors and print the field values to check if they are correctly initialized.

3. Car Class

• Add:
  • A default constructor that sets default values for licensePlate, make, and model.
  • A parameterized constructor that takes licensePlate, make, and model as arguments.
• Instructions for Testing:
  • In the CarTester class, create instances using both constructors and print the field values to confirm the constructors are working.

4. Movie Class

• Add:
  • A default constructor that initializes movieId, title, and durationMinutes with default values.
  • A parameterized constructor that accepts movieId, title, and durationMinutes as arguments.
• Instructions for Testing:
  • In the MovieTester class, create instances using both constructors and print the field values to verify the updates.

5. Employee Class

• Add:
  • A default constructor that sets default values for employeeId, name, and salary.
  • A parameterized constructor that takes employeeId, name, and salary as arguments.
• Instructions for Testing:
  • In the EmployeeTester class, create instances using both constructors and print the field values to ensure the constructors are functioning correctly.

Summary

These exercises will help reinforce your understanding of constructors in Java, including default constructors, parameterized constructors, and overloading. Testing in the respective Tester classes will confirm that your constructors are correctly implemented and working as expected.

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