Java MCQ Questions and Answers – Test Your Knowledge

Are you preparing for a Java certification or interview? Testing your knowledge with Java MCQ questions and answers is a great way to assess your understanding of core concepts. Below are some commonly asked multiple-choice questions along with explanations to help you strengthen your Java skills.

1. What is the output of the following code?
java
Copy
public class Main {  
    public static void main(String[] args) {  
        System.out.println(10 + 20 + "Java");  
    }  
}  
Options:
A) 30Java
B) 1020Java
C) Compilation Error
D) Runtime Error

Answer: A) 30Java
Explanation: The + operator performs addition first (10 + 20 = 30) and then concatenates with "Java".

2. Which keyword is used to prevent method overriding in Java?
Options:
A) static
B) final
C) abstract
D) private

Answer: B) final
Explanation: The final keyword prevents a method from being overridden in subclasses.

3. What does JVM stand for?
Options:
A) Java Virtual Machine
B) Java Variable Method
C) JRE Virtual Memory
D) Just Virtual Machine

Answer: A) Java Virtual Machine
Explanation: JVM is the runtime engine that executes Java bytecode.

4. Which collection class is synchronized by default?
Options:
A) ArrayList
B) HashSet
C) Vector
D) LinkedList

Answer: C) Vector
Explanation: Vector is thread-safe and synchronized, unlike other collections.

5. What is the default value of a boolean in Java?
Options:
A) true
B) false
C) null
D) 0

Answer: B) false
Explanation: Uninitialized boolean variables default to false.

Practicing Java MCQ questions and answers helps reinforce key concepts. Have more questions or need clarification? Drop them in the comments below!