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[Object Oriented Programming]

Which of the following is a valid prototype of the non-parameterised constructor for the class Book?

ID: #24947 Competency focused Practice Questions ISC Class XII Computer Science 3 views

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A public class Book {} ✔ ✖
B Book(void) ✔ ✖
C public Book() ✔ ✖
D public Book(void) ✔ ✖

Correct Answer: Option C

Explanation

[Object Oriented Programming]

Which of the following is a valid prototype of the non-parameterised constructor for the class Book?

(a) public class Book {}

(b) Book(void)

(d) public Book(void)

Correct Answer: (c) public Book()

Understanding Constructor:

A constructor in Java is a special method that:

Has the same name as the class
Does NOT have any return type
Is used to initialize objects

Non-Parameterized Constructor:

A non-parameterized constructor does not take any arguments.

public Book() { // constructor body }

Important Rules:

Constructor name must be same as class name → Book
No return type (not even void)
No parameters inside parentheses

Checking Each Option:

(a) → This is a class declaration, not a constructor ❌
(b) → Using void makes it invalid ❌
(c) → Correct constructor syntax ✔
(d) → Constructor cannot have void ❌

Correct Constructor Example:

class Book { public Book() { System.out.println("Constructor called"); } }

Conclusion:

The correct prototype of a non-parameterized constructor is:

public Book()

Therefore, the correct answer is: (c)

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Q [Object Oriented Programming] Which of the following is a valid prototype of the non-parameterised constructor for the class Book?