Java中应用Executors来建立Thread pool

有时候您需要建立一堆Thread来执行一些小任务，然而频繁的建立Thread有时会是个开销，因为Thread的建立必须与作业系统互动，如果能建立一个Thread pool来管理这些小的Thread并加以重复使用，对于系统效能会是个改善的方式。

您可以使用Executors来建立Thread pool，Executors有几个static方法，列出如下：?

newSingleThreadExecutor

• ExecutorDemo.java

  package onlyfun.caterpillar;import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;public class ExecutorDemo {public static void main(String[] args) {ExecutorService service = Executors.newFixedThreadPool(5);for(int i = 0; i < 10; i++) {final int count = i;service.submit(new Runnable() {public void run() {System.out.println(count);try {Thread.sleep(2000);} catch (InterruptedException e) {e.printStackTrace();}}});}service.shutdown(); // 最后记得关闭Thread pool}}

  
  submit()方法也接受实作Callable介面的物件，最后传回Future物件，可以取得Callable执行过后的传回结果。
  
  如果想利用Executors进行排程，例如排定某个工作30秒后执行：
  ??? ??? ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor( );
  ??? ??? scheduler.schedule(new Runnable( ) {
  ??? ??? ?????????????????????? public void run() {
  ??? ??? ?????????????????????????? // 排程工作
  ??? ??? ?????????????????????? }
  ??? ??? ?????????????????? },?
  ??? ??? ?????????????????? 30, TimeUnit.SECONDS);
  
  或排定某个工作5秒后执行，之后每30秒执行一次：
  ??? ??? ScheduledExecutorService scheduler = Executors.newSingleThreadScheduledExecutor( );
  ??? ??? final ScheduledFuture future = scheduler.scheduleAtFixedRate(new Runnable( ) {
  ??? ??? ?????????????????????? public void run() {
  ??? ??? ?????????????????????????? // 排程工作
  ??? ??? ??????????????????? ??? ?? System.out.println("t");
  ??? ??? ?????????????????????? }
  ??? ??? ?????????????????? },?
  ??? ??? ?????????????????? 0, 5, TimeUnit.SECONDS);
  ??? ????
  ??? ??? // 排定 60 秒后取消future
  ??? ??? scheduler.schedule(new Runnable( ) {
  ??? ??????? public void run( ) {
  ??? ????????? future.cancel(false);
  ??? ??????? }
  ??? ????? }, 60, TimeUnit.SECONDS);
  
  
  如上所示，想要取消排程任务，可以呼叫ScheduledFuture的cancel()方法。

  来源：http://blog.csdn.net/HuDon/article/details/1922563