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Interrupting a Thread in Java

In Java, interrupting threads can be a powerful technique to control their execution. By calling the interrupt() method on a thread, you can force it to exit the sleeping or waiting state and trigger an InterruptedException. When dealing with threads that are currently in a waiting or sleeping state as a result of methods like sleep() or wait() being called, this is especially helpful.

It is crucial to comprehend how the interrupt() method behaves in order to successfully interrupt a thread. An InterruptedException will be immediately thrown when this method is called on a thread that is waiting or sleeping, causing the thread to awaken and handle the exception. This enables the thread to take appropriate actions when interrupted, like cleaning up resources or terminating gracefully.

However, it is crucial to note that calling interrupt() on a thread not in a waiting or sleeping state will not forcibly stop its execution. Instead, the thread's interrupt flag will be set to true, enabling it to respond to the interruption later on in its execution. This can be particularly useful for threads that are performing lengthy computations or tasks and need to respond to the interruption at a convenient time.

To interrupt a sleeping or waiting thread, you can utilize the interrupt() method provided by the Thread class. The thread's current state will be effectively interrupted by this method, and it will throw an InterruptedException if the thread is stuck in a sleep() or wait() call.

In summary, interrupting threads in Java offers a powerful way to manage their execution and gracefully handle interruptions. By understanding the behavior of the interrupt() method and its effect on threads in different states, you can design more robust and responsive multi-threaded applications.

The Thread class provides three methods for interrupting a thread

public void interrupt()

public static boolean interrupted()

public boolean isInterrupted()

Example of Interrupting a thread that doesn't stop working

We handle the InterruptedException in the below program with a try and catch block, so that anytime another thread interrupts the presently operating thread, it would wake up but not stop functioning.

package DockerTpoint;
class ThreadClass extends Thread {
	public void run(){
		try{
			for (int i = 0; i < 3; i++) {
				System.out.println("ThreadClass Thread is running");
				 // The current thread is put to sleep, and another thread is given the opportunity to execute.
				Thread.sleep(1000);
			}
		}
		catch (InterruptedException e) {
			e.printStackTrace();
		}
	}
}
class Main {
	public static void main(String[] args)throws InterruptedException{
		ThreadClass thread = new ThreadClass();
		thread.start();
		thread.interrupt();
		System.out.println("The main thread has finished its execution.");
	}
}

Output:

The main thread has finished its execution.
ThreadClass Thread is running
java.lang.InterruptedException: sleep interrupted

Example of Interrupting a thread that stops working

In the program below, after interrupting the currently executing thread, we throw a new exception in the catch block, causing it to stop working.

package DockerTpoint;
class ThreadClass extends Thread {
	public void run(){
		try{
			Thread.sleep(1000);
			System.out.println("ThreadClass");
		}
		catch (InterruptedException e) {
			throw new RuntimeException("Thread interrupted"+e);  
		}
	}
}
class Main {
	public static void main(String[] args)throws InterruptedException{
		ThreadClass thread = new ThreadClass();
		thread.start();
		try {
			thread.interrupt();
		} catch (Exception e) {
			e.printStackTrace();
		}
	}
}

Output:

Exception in thread "Thread-0" java.lang.RuntimeException: Thread 
    interruptedjava.lang.InterruptedException: sleep interrupted

Example of Interrupting a thread that works normally

In the program below, after interrupting the currently executing thread, we throw a new exception in the catch block, causing it to stop working.

class ThreadClass extends Thread {
	public void run(){
		for (int i = 1; i <= 10; i++) {
			System.out.println("5 * "+i+" = "+5*i);
		}
	}
}
class Main {
	public static void main(String[] args){
		ThreadClass thread = new ThreadClass();
		thread.start();
		thread.interrupt();
	}
}

Output:

5 * 1 = 5
5 * 2 = 10
5 * 3 = 15
5 * 4 = 20
5 * 5 = 25
5 * 6 = 30
5 * 7 = 35
5 * 8 = 40
5 * 9 = 45
5 * 10 = 50

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Interrupting a Thread in Java

The Thread class provides three methods for interrupting a thread

Example of Interrupting a thread that doesn't stop working

Example of Interrupting a thread that stops working

Example of Interrupting a thread that works normally

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