Java Constructor - Exercises, Practice, Solution

Java Constructors Exercises [10 exercises with solution]

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1. Default Constructor:
Write a Java program to create a class called "Cat" with instance variables name and age. Implement a default constructor that initializes the name to "Unknown" and the age to 0. Print the values of the variables.

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2. Parameterized Constructor:
Write a Java program to create a class called Dog with instance variables name and color. Implement a parameterized constructor that takes name and color as parameters and initializes the instance variables. Print the values of the variables.

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3. Constructor Overloading
Write a Java program to create a class called "Book" with instance variables title, author, and price. Implement a default constructor and two parameterized constructors:

• One constructor takes title and author as parameters.
• The other constructor takes title, author, and price as parameters.
• Print the values of the variables for each constructor.

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4. Chaining Constructors
Write a Java program to create a class called Student with instance variables studentId, studentName, and grade. Implement a default constructor and a parameterized constructor that takes all three instance variables. Use constructor chaining to initialize the variables. Print the values of the variables.

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5. Write a Java program to create a class called "Book" with attributes for title, author, and ISBN, and methods to add and remove books from a collection.

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6. Constructor with Validation
Write a Java program to create a class called Account with instance variables accountNumber and balance. Implement a parameterized constructor that initializes these variables with validation:

• accountNumber should be non-null and non-empty.
• balance should be non-negative.
• Print an error message if the validation fails.

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7. Constructor with Default Values
Write a Java program to create a class called Car with instance variables make, model, and year. Implement a parameterized constructor that initializes these variables and assigns default values if not provided. Print the values of the variables.

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8. Overloading Constructors with Different Data Types
Write a Java program to create a class called Point with instance variables x and y. Implement overloaded constructors:

• One constructor takes int parameters.
• Another constructor takes double parameters.
• Print the values of the variables for each constructor.

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9. Constructor with Array Initialization
Write a Java program to create a class called Classroom with instance variables className and students (an array of strings). Implement a parameterized constructor that initializes these variables. Print the values of the variables.

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10. Constructor for Singleton Pattern
Write a Java program to create a class called Singleton that ensures only one instance of the class can be created. Implement a private constructor and a public static method to get the single instance of the class. Print a message indicating the creation of the instance.

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