CODEWITHSUNDEEP
javaexceptiontry-catch
Forrest
Forrest

Reputation: 607

What does this try and catch method do?

try 
{
    Thread.sleep(5000);
} catch (InterruptedException e) {
     e.printStackTrace();
}

I understand what the first part is doing. But what is the catch part waiting for? Like what needs to happen to execute this part.

Upvotes: 1

Views: 149

Answers (8)

Bill Stidham
Bill Stidham

Reputation: 1480

This is relevant to multithreaded applications.When you have reference to an object of a class that either implements Runnable or extends Thread, and inside that object, a Thread.sleep(i) method has been idling the process, you can call reference.interupt() on that reference and it will trigger the InterruptedException. Here's an example:

In the below code, the Scratch class's run method goes to sleep for 60000 ms (or 1 minute) and prints "I've been interrupted" if it receives an InterruptedExection. The way the code is written, it will not receive this exception and will sleep the entire time. But run it a second time with the line //scratch.interrupt(); uncommented and see what happens. 

package scratch;
/**
 *
 * @author bstidham
 */
public class Scratch extends Thread {

    public void run() {
        System.out.println("Hello from a thread!");
        System.out.println("Going to sleep for 1 minute...");
        try {
            Thread.sleep(60000);
        } catch (InterruptedException e) {
            System.out.println("I've been interrupted!");
        }
        System.out.println("Awake now");
    }

    public static void main(String args[]) {
        Scratch scratch = new Scratch();
        scratch.start();
        //scratch.interrupt();
    }
}

Upvotes: 0

AJ.
AJ.

Reputation: 4534

public class InterruptedException
extends Exception

Thrown when a thread is waiting, sleeping, or otherwise occupied, and the thread is interrupted, either before or during the activity. Occasionally a method may wish to test whether the current thread has been interrupted, and if so, to immediately throw this exception.

Best Explanation is Given ╠══ HERE

Upvotes: 1

Olivier Croisier
Olivier Croisier

Reputation: 6149

Every piece of code is run by a "thread". You can think of that as a little virtual processor dedicated to running that particular piece of code.

By calling the Thread.sleep() method, you put this thread in the WAITING state for a certain amount of time. While WAITING, the thread cannot do anything, and in particular, it cannot "hear" calls from other threads.

The only way to wake up the thread and having it run its code again, is to sent it an interruption, which is a very strong signal. This is done by calling the interrupt() method of this thread, from another thread.

When waked up, the thread goes to the RUNNING state again, but to signal the developer that it was waked up earlier than expected, it throws an InterruptedException, which is a checked exception. This is why you have to catch it and deal with it.

Upvotes: 1

Churk
Churk

Reputation: 4637

You thread is going to sleep for 5 seconds.

If another thread tries to wake this thread up (Interrupt). It will end up in the exception block and your stacktrace will be printed.

Upvotes: 1

Konstantin Yovkov
Konstantin Yovkov

Reputation: 62884

Because the Thread#sleep() method is defined to throw an InterruptedException under some circumstances, the developer should take care of it when this exact exception occurs. This is why the catch block is needed - to hold the logic which handles the InterruptedException

Upvotes: 1

Someone
Someone

Reputation: 551

The sleep method halts execution of the current thread, in your case 5000 milliseconds (5 seconds). This method however throws InterruptedException which has to be caught.

Upvotes: 1

Kick
Kick

Reputation: 4923

If the Thread is interrupted then it will throw the exception and it will be catched in the catch block.

Upvotes: 0

Ruchira Gayan Ranaweera
Ruchira Gayan Ranaweera

Reputation: 35597

If InterruptedException throws(Thread interruption may cause this) from try block that will catch by catch block and as you define in the catch block,it will print the Exception stack trace.

Upvotes: 0

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