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Java wait,join,notify解析

 3 years ago
source link: https://1fishman.github.io/2019/06/22/Java-wait-join-notify%E8%A7%A3%E6%9E%90/
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Java wait,join,notify解析

2019-06-22

|

2019-07-01

| Views: 20

wait()

wait()方法只能在对象上调用,比如 obj.wait(),表明将当前线程阻塞,直到有其他线程调用此对象的notify()或notifyAll()方法.线程才会继续执行. 或者有其他线程中断了此线程,将会抛出一个中断异常.

wait(long timeout)

和wait()方法类似,但是此等待是有超时限制的,当等待的时间到了,也会自动被唤醒

wait(long timeout,int nanos)

此方法就有点意思了,看名字好像等待超时时间的控制精确到了纳秒级别,但是看看源码就了解到了,事实并不是如此.

public final void wait(long timeout, int nanos) throws InterruptedException {
    if (timeout < 0) {
        throw new IllegalArgumentException("timeout value is negative");
    }
    if (nanos < 0 || nanos > 999999) {
        throw new IllegalArgumentException(
                            "nanosecond timeout value out of range");
    }
    if (nanos > 0) {
        timeout++;
    }
    wait(timeout);
}

可以看到,如果nanos大于0,则直接将timeout++,也就是说如果有设置纳秒参数,则再加1毫秒.所以,等待超时只能精确到毫秒级别

notify

notify就很简单了,就是随机唤醒一个在此对象上等待的线程.

notifyAll()

All就是所有,就是唤醒在此对象上等待的线程

yield

他是thread的静态方法,对当前线程有效
yield()方法,此方法就是让出cpu的执行权,意思就是我不干了,你们谁有事谁就干吧.让出执行权,让其他线程去干活.
但是这个让出指的是让所有的线程重新争夺cpu的执行权,包括自己,所以,还是有可能继续轮到自己干的.

join()

join方法是在Thread类中的方法,调用join方法就是等待此线程执行完成,之后再执行.比如下面代码:

public static void main(String[] args) throws InterruptedException {
    int a = 10;
    Thread thread1= new Thread(new Runnable() {
        @Override
        public void run() {
            for (int i = 0; i < 100; i++) {
                // 省略代码
        }
    });
    thread1.start();
    thread1.join();
}

在这里调用thread1.join()方法,就会将当前线程阻塞,知道thread1()完成返回之后才会继续执行


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