Java by API/java.util.concurrent/Executors

Executors: newFixedThreadPool(int nThreads)

 
import java.io.IOException;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.TimeUnit;
public class MainClass {
  ExecutorService executor = Executors.newFixedThreadPool(3);
  public void start() throws IOException {
    int i=0;
    while (!executor.isShutdown())
      executor.submit(new MyThread(i++));
  }
  public void shutdown() throws InterruptedException {
    executor.shutdown();
    executor.awaitTermination(30, TimeUnit.SECONDS);
    executor.shutdownNow();
  }
  public static void main(String argv[]) throws Exception {
    new MainClass().start();
  }
}
class MyThread implements Runnable {
private int i;
  MyThread(int i) {
  this.i = i;
  }
  public void run() {
    System.out.println("I am in thread:"+i);
    
  }
}

Executors: newSingleThreadScheduledExecutor()

 
/*
License for Java 1.5 "Tiger": A Developer"s Notebook
     (O"Reilly) example package
Java 1.5 "Tiger": A Developer"s Notebook (O"Reilly) 
by Brett McLaughlin and David Flanagan.
ISBN: 0-596-00738-8
You can use the examples and the source code any way you want, but
please include a reference to where it comes from if you use it in
your own products or services. Also note that this software is
provided by the author "as is", with no expressed or implied warranties. 
In no event shall the author be liable for any direct or indirect
damages arising in any way out of the use of this software.
*/

import static java.util.concurrent.TimeUnit.SECONDS;
import java.io.PrintStream;
import java.util.Date;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.ScheduledFuture;
public class Main {
  public static void main(String[] args) {
    // Get the scheduler
    ScheduledExecutorService scheduler =
      Executors.newSingleThreadScheduledExecutor();
    // Get a handle, starting now, with a 10 second delay
    final ScheduledFuture<?> timeHandle =
      scheduler.scheduleAtFixedRate(new TimePrinter(System.out), 0, 10, SECONDS);    
    // Schedule the event, and run for 1 hour (60 * 60 seconds)
    scheduler.schedule(new Runnable() {
      public void run() {
        timeHandle.cancel(false);
      }
    }, 60*60, SECONDS);

    /**
     * On some platforms, you"ll have to setup this infinite loop to see output
    while (true) { }
     */
  }
}
class TimePrinter implements Runnable {
  private PrintStream out;
  public TimePrinter(PrintStream out) {
    this.out = out;
  }
  public void run() {
    out.printf("Current time: %tr%n", new Date());
  }
}