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Java Threads & Concurrency Interview Questions

MCQ Question 1 of 10

Question 1: JAVA - Thread Creation

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

Extend the Thread classImplement the Runnable interfaceUse Executors.newFixedThreadPool()All of the above

Question 2: JAVA - Start vs Run

What happens if you call the run() method directly instead of start() on a thread?

A new thread startsThe method runs in the current threadCompilation errorRuntime exception

Question 3: JAVA - Runnable Example

What will this code print?

class MyTask implements Runnable {
    public void run() {
        System.out.println("Task executed");
    }
}
public class Test {
    public static void main(String[] args) {
        Thread t = new Thread(new MyTask());
        t.start();
    }
}

NothingTask executedCompilation errorRuntime exception

Question 4: JAVA - Sleep Method

What does Thread.sleep(1000) do?

Terminates the threadSuspends thread foreverPauses the thread for 1 secondPuts all threads to sleep

Question 5: JAVA - Synchronization

Why is synchronization used in multithreading?

To make code fasterTo prevent deadlocksTo control access to shared resourcesTo allow multiple threads to write simultaneously

Question 6: JAVA - Deadlock Example

What is a deadlock?

When two threads wait for each other’s locksWhen a thread never terminatesWhen the JVM crashesWhen multiple threads execute simultaneously

Question 7: JAVA - Executor Framework

Which class provides factory methods for creating thread pools?

ThreadRunnableExecutorsThreadPool

Question 8: JAVA - Callable vs Runnable

Which is true about Callable vs Runnable?

Runnable returns a result, Callable does notCallable returns a result and can throw exceptionsBoth are identicalRunnable works only with ExecutorService

Question 9: JAVA - Volatile Keyword

What does the volatile keyword ensure in Java?

Atomicity of operationsThread safety automaticallyVisibility of changes across threadsSynchronization

Question 10: JAVA - ReentrantLock Example

Which advantage does ReentrantLock have over synchronized?

Fairness policyAbility to try lock without waitingInterruptible lock acquisitionAll of the above