Java Multiple Choice Questions (MCQs)

1. Core Java

Q1. Which of the following is true about the final keyword in Java?

• A) A final class can be subclassed.
• B) A final method can be overridden.
• C) A final variable's value cannot be changed once assigned.
• D) final is used to define interfaces.

Answer: C. A final variable acts as a constant and its value cannot be modified once initialized.

Q2. What is the size of int data type in Java?

• A) 16 bits
• B) 32 bits
• C) 64 bits
• D) Depends on execution environment

Answer: B. In Java, int is always 32 bits (4 bytes) regardless of the underlying platform architecture.

2. Object-Oriented Programming

Q3. Which of these cannot be used for a variable name in Java?

• A) identifier & keyword
• B) identifier
• C) keyword
• D) none of the mentioned

Answer: C. Keywords are reserved words in Java and cannot be used as variable names.

Q4. What is the process of defining more than one method in a class with the same name but different parameters?

• A) Method overriding
• B) Method overloading
• C) Method hiding
• D) Encapsulation

Answer: B. Method overloading allows multiple methods to have the same name but different parameter lists.

3. Collections & Generics

Q5. Which collection class allows you to associate its elements with key values, and does not allow duplicate keys?

• A) java.util.Set
• B) java.util.List
• C) java.util.Map
• D) java.util.Queue

Answer: C. The Map interface maps keys to values, and a map cannot contain duplicate keys.