Executorservice

public interface ExecutorService extends Executor

An Executor that provides methods to manage termination and methods that can produce a Future for tracking progress of one or more asynchronous tasks.

The following example includes two classes. PrintTask.java creates threads that sleep for a random time (0-5 secs). RunnableTester.java executes the PrintTask threads using a fixed thread pool.

PrintTask.java

// PrintTask class sleeps for a random time from 0 to 5 seconds
import java.util.Random;
 
class PrintTask implements Runnable
{
    private int sleepTime; // random sleep time for thread
 
    private String threadName; // name of thread
 
    private static Random generator = new Random();
 
    // assign name to thread
    public PrintTask(String name)
    {
        threadName = name; // set name of thread
 
        // pick random sleep time between 0 and 5 seconds
        sleepTime = generator.nextInt(5000);
    } // end PrintTask constructor
 
    {
        // TODO Auto-generated constructor stub
    }
 
    // method run is the code to be executed by new thread
    public void run()
    {
        try
        // put thread to sleep for sleepTime amount of time
        {
            System.out.printf("%s going to sleep for %d milliseconds.\n",
                    threadName, sleepTime);
 
            Thread.sleep(sleepTime); // put thread to sleep
        } // end try
        // if thread interrupted while sleeping, print stack trace
        catch (InterruptedException exception)
        {
            exception.printStackTrace();
        } // end catch
 
        // print thread name
        System.out.printf("%s done sleeping\n", threadName);
    } // end method run
} // end class PrintTask<

RunnableTester.java

/*
 * Runnables are executed by an object of a class that implements the Executor interface.
 * This interfaces declares the method execute(Runnable). This method creates a new thread
 * and launches it immediately.
 */
import java.util.concurrent.Executors;
import java.util.concurrent.ExecutorService;
 
public class RunnableTester
{
    public static void main(String[] args)
    {
        // create and name each runnable
        PrintTask task1 = new PrintTask("thread1");
        PrintTask task2 = new PrintTask("thread2");
        PrintTask task3 = new PrintTask("thread3");
 
        System.out.println("Starting threads");
 
        // create ExecutorService to manage threads
        ExecutorService threadExecutor = Executors.newFixedThreadPool(3);
 
        // start threads and place in runnable state
        threadExecutor.execute(task1); // start task1
        threadExecutor.execute(task2); // start task2
        threadExecutor.execute(task3); // start task3
 
        threadExecutor.shutdown(); // shutdown worker threads
 
        System.out.println("Threads started, main ends\n");
    } // end main
} // end class RunnableTester

See also:

• SheduledExecutorService
• Executor
• Executors