JAVA EE: Java Tutorial: Java Threads (Cached Thread pool in java

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Java Tutorial: Java Threads (Cached Thread pool in java | Java cached thread pool)

ThreadPoolTest.java

import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Future;

public class ThreadPoolTest
{
    public static void main(String[] args)
    {
        int numOfCallableTasks = 4;

        ExecutorService executorService = Executors.newCachedThreadPool();
        CallableTask callableTasks[] = new CallableTask[numOfCallableTasks];
        Future<?> futures[] = new Future[numOfCallableTasks];

        for (int i = 0; i < numOfCallableTasks; i++)
        {
            callableTasks[i] = new CallableTask(i);
            futures[i] = executorService.submit(callableTasks[i]);
        }
        for (int i = 0; i < numOfCallableTasks; i++)
        {
            try
            {
                System.out.println("Ending task : " + futures[i].get());
            }
            catch (Exception e)
            {
                e.printStackTrace();
            }
        }
    }
}

CallableTask.java

import java.util.concurrent.Callable;

public class CallableTask implements Callable<Integer>
{
    private int taskNumber;

    CallableTask(int taskNumber)
    {
        this.taskNumber = taskNumber;
    }

    public Integer call()
    {
        for (int i = 0; i <= 100; i += 20)
        {
            // Perform some work ...
            System.out.println(Thread.currentThread().getName()
                    + " taskNumber : " + taskNumber + ", percent complete: "
                    + i);
            try
            {
                Thread.sleep((int) (Math.random() * 1000));
            }
            catch (InterruptedException e)
            {
            }
        }
        return (taskNumber);
    }
}

Output

pool-1-thread-2 taskNumber : 1, percent complete: 0
pool-1-thread-1 taskNumber : 0, percent complete: 0
pool-1-thread-3 taskNumber : 2, percent complete: 0
pool-1-thread-4 taskNumber : 3, percent complete: 0
pool-1-thread-2 taskNumber : 1, percent complete: 20
pool-1-thread-4 taskNumber : 3, percent complete: 20
pool-1-thread-1 taskNumber : 0, percent complete: 20
pool-1-thread-3 taskNumber : 2, percent complete: 20
pool-1-thread-4 taskNumber : 3, percent complete: 40
pool-1-thread-3 taskNumber : 2, percent complete: 40
pool-1-thread-2 taskNumber : 1, percent complete: 40
pool-1-thread-4 taskNumber : 3, percent complete: 60
pool-1-thread-3 taskNumber : 2, percent complete: 60
pool-1-thread-2 taskNumber : 1, percent complete: 60
pool-1-thread-1 taskNumber : 0, percent complete: 40
pool-1-thread-2 taskNumber : 1, percent complete: 80
pool-1-thread-3 taskNumber : 2, percent complete: 80
pool-1-thread-2 taskNumber : 1, percent complete: 100
pool-1-thread-4 taskNumber : 3, percent complete: 80
pool-1-thread-1 taskNumber : 0, percent complete: 60
pool-1-thread-4 taskNumber : 3, percent complete: 100
pool-1-thread-3 taskNumber : 2, percent complete: 100
pool-1-thread-1 taskNumber : 0, percent complete: 80
pool-1-thread-1 taskNumber : 0, percent complete: 100
Ending task : 0
Ending task : 1
Ending task : 2
Ending task : 3