What happens if start() is called twice on the same thread? Java class MyThread extends Thread { public void run() { System.out.println("Running..."); } public static void main(String[] args) { MyThread t = new MyThread(); t.start(); t.start(); } }

Throws IllegalThreadStateException

Tutorials
Courses

Java Thread Basics and Lifecycle

Here are 10 essential multiple-choice questions on Java Thread Basics and Lifecycle, covering key concepts.

Last Updated :

Discuss

Comments

Question 1

Which of the following is the correct way to create a thread in Java?

Extending the Thread class
Implementing the Runnable interface
Both A and B
Using the Callable interface only

Discuss it

Question 2

What will be the output of the following code?

Java

class MyThread extends Thread {
    public void run() {
        System.out.println("Thread is running");
    }

    public static void main(String[] args) {
        MyThread t = new MyThread();
        t.run();
    }
}

Thread is running
Compilation Error
No Output
Runtime Exception

Discuss it

Question 3

Which method is used to start a thread in Java?

run()
start()
execute()
begin()

Discuss it

Question 4

What is the initial state of a thread when it is created but not yet started?

NEW
RUNNABLE
BLOCKED
WAITING

Discuss it

Question 5

Which of the following statements about the Runnable interface is true?

It contains the start() method
It contains the run() method
It can only be implemented by a class that extends Thread
It cannot be used for multithreading

Discuss it

Question 6

What happens if start() is called twice on the same thread?

Java

class MyThread extends Thread {
    public void run() {
        System.out.println("Running...");
    }
    
    public static void main(String[] args) {
        MyThread t = new MyThread();
        t.start();
        t.start();
    }
}

Thread runs twice
Compiles and runs normally
Throws IllegalThreadStateException
No output

Discuss it

Question 7

Which of the following is NOT a valid thread state in Java?

NEW
TERMINATED
RUNNING
TIMED_WAITING

Discuss it

Question 8

What happens if sleep(1000) is called inside a thread?

Thread execution is paused for 1 second
Thread is terminated
Thread goes to NEW state
Thread execution continues immediately

Discuss it

Question 9

What will be the output of the following code?

Java

class Geeks {
    public static void main(String[] args) {
        Thread t = new Thread(() -> System.out.println("Hello from Thread"));
        t.start();
    }
}

Hello from Thread
Compilation Error
No Output
Runtime Exception

Discuss it

Question 10

Which method is used to wait for a thread to finish execution?

wait()
sleep()
join()
yield()

Discuss it

Tags:

Java Quiz

There are 10 questions to complete.

Take a part in the ongoing discussion