JAVA MCQs with answers Page - 376

Dear candidates you will find MCQ questions of JAVA here. Learn these questions and prepare yourself for coming examinations and interviews. You can check the right answer of any question by clicking on any option or by clicking view answer button.
Share your questions by clicking Add Question

📊 JAVA
Q. Which of the following is thread-safe?
  • (A) ArrayList
  • (B) HashMap
  • (C) Vector
  • (D) HashSet
💬 Discuss
✅ Correct Answer: (C) Vector

Explanation: Vector is synchronized and thread-safe.

📊 JAVA
Q. Which keyword is used to refer to current object?
  • (A) this
  • (B) super
  • (C) self
  • (D) object
💬 Discuss
✅ Correct Answer: (A) this

Explanation: 'this' refers to the current object instance.

📊 JAVA
Q. Which exception is unchecked?
  • (A) IOException
  • (B) SQLException
  • (C) NullPointerException
  • (D) ClassNotFoundException
💬 Discuss
✅ Correct Answer: (C) NullPointerException

Explanation: NullPointerException is an unchecked exception.

📊 JAVA
Q. What will be the output?
Code: 
System.out.println(5 + 5 + "5" + 5 + 5);
  • (A) 10555
  • (B) 10555
  • (C) 10555
  • (D) 10555
💬 Discuss
✅ Correct Answer: (A) 10555

Explanation: 5+5=10, then string concatenation results in 10555.

📊 JAVA
Q. What is the size of int in Java?
  • (A) 2 bytes
  • (B) 4 bytes
  • (C) Depends on OS
  • (D) 8 bytes
💬 Discuss
✅ Correct Answer: (B) 4 bytes

Explanation: int is always 4 bytes (32-bit) in Java, regardless of platform.

📊 JAVA
Q. Which memory area stores class metadata?
  • (A) Heap
  • (B) Stack
  • (C) Method Area
  • (D) PC Register
💬 Discuss
✅ Correct Answer: (C) Method Area

Explanation: Class metadata is stored in Method Area (part of JVM).

📊 JAVA
Q. What will be the output?
Code: 
Integer a = 127;
Integer b = 127;
System.out.println(a == b);
  • (A) true
  • (B) false
  • (C) Compilation Error
  • (D) Runtime Error
💬 Discuss
✅ Correct Answer: (A) true

Explanation: Integer cache works for values -128 to 127, so both refer to same object.

📊 JAVA
Q. Which keyword is used to create a thread?
  • (A) Runnable
  • (B) Thread
  • (C) Both a and b
  • (D) process
💬 Discuss
✅ Correct Answer: (C) Both a and b

Explanation: Threads can be created by extending Thread or implementing Runnable.

📊 JAVA
Q. Which method is used to start a thread?
  • (A) run()
  • (B) start()
  • (C) execute()
  • (D) init()
💬 Discuss
✅ Correct Answer: (B) start()

Explanation: start() creates a new thread and calls run() internally.

📊 JAVA
Q. Which collection is synchronized?
  • (A) HashMap
  • (B) ArrayList
  • (C) Hashtable
  • (D) HashSet
💬 Discuss
✅ Correct Answer: (C) Hashtable

Explanation: Hashtable is synchronized by default.

Programming Categories

📱 Download Our App

Learn MCQs on the go with our easy-to-use Android app

Get it on Google Play