在Java中,所有的线程都存在于线程组中,每个线程组中可以包含多个线程或者线程组.运行下面的程序,从结果中可以看出默认的线程组层次结构.
system是Java中的根线程组.从system开始,有一层层的线程和线程组.类似目录结构.
/** * Java线程组的结构,见运行结果 * @author Administrator * */ public class Main { public static void main(String [] args) { Thread.currentThread().getThreadGroup().getParent().list(); Thread.currentThread().getThreadGroup().list(); } }
下面的程序中实现当一个线程运行结束时,结束其他的线程.这个需求也可以用Executor框架来完成.不过显然用线程组是容易的.
/** * 实现当一个线程运行结束时,结束其他的线程 * @author Administrator * */ public class Main { public static void main(String [] args) throws InterruptedException{ ThreadGroup threadGroup = new ThreadGroup("Searcher"); for(int i=0;i<5;i++){ new Thread(threadGroup,new Task(),"t"+(i+1)).start(); } System.out.println(threadGroup.activeCount()); threadGroup.list(); Thread.sleep(1000); waitFinish(threadGroup); threadGroup.interrupt(); } private static void waitFinish(ThreadGroup threadGroup) { while (threadGroup.activeCount()>5) { } System.out.println("有一个结束了"); } } class Task implements Runnable { public void run() { for(int i=0;i<Integer.MAX_VALUE/100;i++){ System.out.print(i+" "); if(Thread.currentThread().isInterrupted()) break; } System.out.println(Thread.currentThread().getName()); } }
在JAVA多线程编程时,通过为一个线程对象或者一个线程类设置UncaughtExceptionHandler可以实现捕获run()方法内的运行时异常.
下面的例子是捕获线程内的运行时异常:
public class Main { public static void main(String [] args) { for(int i=0;i<3;i++){ final int flag=i; MyThread myThread=new MyThread(); myThread.setUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() { @Override public void uncaughtException(Thread arg0, Throwable arg1) { // TODO Auto-generated method stub System.out.println("mythead发生异常!"+flag); } }); myTHread.start(); } } } class MyThread extends Thread{ public void run(){ String str=null; try { Thread.sleep(2000); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println(str.hashCode()); } }