Java中使用wait()与notify()实现线程间协作
时间:2011-03-24 zhangjunhd
使用wait()与notify()/notifyAll()可以使得多个任务之间彼 此协作。
1. wait()与notify()/notifyAll()
调用sleep()和yield()的时候锁并没有被释放，而调用wait() 将释放锁。这样另一个任务（线程）可以获得当前对象的锁，从而 进入它的synchronized方法中。可以通过notify()/notifyAll()， 或者时间到期，从wait()中恢复执行。
只能在同步控制方法或同步块中调用wait()、notify()和 notifyAll()。如果在非同步的方法里调用这些方法，在运行时会 抛出IllegalMonitorStateException异常。
2.模拟单个线程对多个线程的唤醒
模拟线程之间的协作。Game类有2个同步方法prepare()和go() 。标志位start用于判断当前线程是否需要wait()。Game类的实例 首先启动所有的Athele类实例，使其进入wait()状态，在一段时间 后，改变标志位并notifyAll()所有处于wait状态的Athele线程。
Game.java
package concurrency;
import java.util.Collection;
import java.util.Collections;
import java.util.HashSet;
import java.util.Iterator;
import java.util.Set;
class Athlete implements Runnable {
private final int id;
private Game game;
public Athlete(int id, Game game) {
this.id = id;
this.game = game;
}
public boolean equals(Object o) {
if (!(o instanceof Athlete))
return false;
Athlete athlete = (Athlete) o;
return id == athlete.id;
}
public String toString() {
return "Athlete<" + id + ">";
}
public int hashCode() {
return new Integer(id).hashCode();
}
public void run() {
try {
game.prepare(this);
} catch (InterruptedException e) {
System.out.println(this + " quit the game");
}
}
}
public class Game implements Runnable {
private Set<Athlete> players = new HashSet<Athlete>();
private boolean start = false;
public void addPlayer(Athlete one) {
players.add(one);
}
public void removePlayer(Athlete one) {
players.remove(one);
}
public Collection<Athlete> getPlayers() {
return Collections.unmodifiableSet(players);
}
public void prepare(Athlete athlete) throws InterruptedException {
System.out.println(athlete + " ready!");
synchronized (this) {
while (!start)
wait();
if (start)
System.out.println(athlete + " go!");
}
}
public synchronized void go() {
notifyAll();
}
public void ready() {
Iterator<Athlete> iter = getPlayers ().iterator();
while (iter.hasNext())
new Thread(iter.next()).start();
}
public void run() {
start = false;
System.out.println("Ready......");
System.out.println("Ready......");
System.out.println("Ready......");
ready();
start = true;
System.out.println("Go!");
go();
}
public static void main(String[] args) {
Game game = n
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