标签:守护线程
本文是学习网络上的文章时的总结,感谢大家无私的分享。
1、Java有两种Thread:“守护线程Daemon”与“用户线程User”。用户线程:Java虚拟机在它所有非守护线程已经离开后自动离开;守护线程:则是用来服务用户线程的,如果没有其他用户线程在运行,那么就没有可服务对象,也就没有理由继续下去。
2、setDaemon(boolean on)方法可以方便的设置线程的Daemon模式,true为Daemon模式,此方法必须在线程启动之前调用,当线程正在运行时调用会产生异常。
3、当一个守护线程中产生了其他线程,那么这些新产生的线程不用设置Daemon属性,都将是守护线程。
4、Java垃圾回收线程就是一个典型的守护线程,当我们的程序中不在有任何运行中的Thread,程序就不会再产生垃圾,垃圾回收器也就无事可做,所以当垃圾回收线程是Java虚拟机上仅剩的线程时,Java虚拟机会自动离开。
package chapter; import java.util.ArrayDeque; import java.util.Deque; public class Main7 { /** * <p> * </p> * @author zhangjunshuai * @date 2014-8-18 上午11:21:30 * @param args */ public static void main(String[] args) { Deque<Event> deque = new ArrayDeque<Event>(); WriterTask writer = new WriterTask(deque); for (int i = 0; i < 3; i++) { Thread thread = new Thread(writer); thread.start(); } CleanerTask cleaner = new CleanerTask(deque); cleaner.start(); } }
package chapter; import java.util.Date; import java.util.Deque; import java.util.concurrent.TimeUnit; public class WriterTask implements Runnable{ private Deque<Event> deque; public WriterTask(Deque<Event> deque) { this.deque = deque; } @Override public void run() { for (int i = 0; i < 100; i++) { Event event = new Event(); event.setDate(new Date()); event.setEvent(String.format("The thread %s has generated an event ", Thread.currentThread().getId())); deque.addFirst(event); try { TimeUnit.SECONDS.sleep(1); } catch (InterruptedException e) { e.printStackTrace(); } } } }
package chapter; import java.util.Date; import java.util.Deque; public class CleanerTask extends Thread{ private Deque<Event> deque; public CleanerTask(Deque<Event> deque){ this.deque = deque; setDaemon(true); } @Override public void run() { while(true){ Date date = new Date(); clean(date); } } private void clean(Date date){ long difference; boolean delete; if(deque.size()==0){ return; } delete = false; do{ Event e = deque.getLast(); difference = date.getTime()-e.getDate().getTime(); if(difference>10000){ System.out.printf("Cleaner: %s\n", e.getEvent()); deque.removeLast(); delete =true; } }while(difference>10000); if(delete){ System.out.printf("Cleaner:Size of the queue:%d\n", deque.size()); } } }
Java并发学习之七——守护线程,布布扣,bubuko.com
标签:守护线程
原文地址:http://blog.csdn.net/junshuaizhang/article/details/38711799