Callable and Future in Java

If a Thread require to return something after execution Callable interface. Callable interface contain only one method.

  public Object call() throws Exception {
        return null;
    }

If a Callable object is submit to executor then after completing the job Thread returns and opbject of typr Future that is Future object can be used to retrive result from callable jobs.

import java.util.concurrent.*;

public class CallableExample implements Callable {

    int number;
    public CallableExample(int number) {
        this.number = number;
    }
    @Override
    public Object call() throws Exception {
        System.out.println(Thread.currentThread().getName() + " Is responsible to calculate square of given number " + number );
        return number* number;
    }}
class CallableExampleRun{
    public static void main(String[] args) throws ExecutionException, InterruptedException {
        CallableExample [] tasks = {new CallableExample(3),new CallableExample(4),new CallableExample(5), new CallableExample(6),new CallableExample(7)};
        ExecutorService service = Executors.newFixedThreadPool(3);
        for(CallableExample task : tasks){
            Future future = service.submit(task);
            System.out.println(future.get());
        }
        service.shutdown();
    }
}

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