Java 线程中的Join、wait、notify，sleep

1.wait和notify
这两个方法都是Object中的方法,放在一块是因为他们关系非常密切.
wait就是等待这个对象的同步锁,不过调用这个方法必须先获得这个对象的同步锁,就这一点很多人就搞晕了.
这里先解释一下这两个方法,然后给出一个小例子说明.
wait:等待对象的同步锁,需要获得该对象的同步锁才可以调用这个方法,否则后收到一个 IllegalMonitorStateException,这个是运行时异常.调用这个方法后,就放弃了这个同步锁了.如果不带参数的wait方法就只 有等别人唤醒了,如果带一个参数的
化就设置等待最长时间,过了这个时间即使没有人唤醒这个线程也不再等待了.
notify:唤醒在等待该对象同步锁的线程(只唤醒一个,如果有多个在等待),但是notifyAll可以唤醒所有等待的线程,注意唤醒的时在notify之前wait的线程,之后的没有效果.
这里举一个通俗的例子,两个人共有一个卫生间(每次只能一个人用),他们都要刷牙和方便,他们是这样约定的,轮流用,第一个人先刷牙,然后第二个人刷牙…

class Syn{        public static void main(String[] args) throws Exception        {            TwoPeople.ONE.start();            TwoPeople.TWO.start();        }}class TwoPeople extends Thread{    private int i=0;    static Thread ONE=new TwoPeople(1);    static Thread TWO=new TwoPeople(2);    static Object washroom=new Object();        private TwoPeople(int i){this.i=i;}    public void run(){        synchronized(washroom){            try{                if(i==1){                    brush(); //1                   washroom.wait(); //2                    release(); //6                       washroom.notify(); //7                }            else{                    brush(); //3                    washroom.notify(); //4                    washroom.wait(); //5                    release(); //8            }            }catch(InterruptedException e){e.printStackTrace();}        }    }    private void brush() {            System.out.println("People "+i+" is brushing !");             try{Thread.sleep(2000);}catch(InterruptedException e){e.printStackTrace();}            //延迟两秒看效果            System.out.println("People "+i+" has burshed !");    }    private void release(){            System.out.println("People "+i+" is releasing !");            try{Thread.sleep(2000);}catch(InterruptedException e){e.printStackTrace();}            //延迟两秒看效果            System.out.println("People "+i+" has released !");    }};

People 1 is brushing !
People 1 has burshed !
People 2 is brushing !
People 2 has burshed !
People 1 is releasing !
People 1 has released !
People 2 is releasing !
People 2 has released !
上面的代码很简短,而且表明了执行顺序,至于join和sleep还是下次再讨论吧.