多线程中其他的两个API：Thread.yield和(Thread).join

Thread.yield

此⽅法可以向操作系统提出建议，优先去执⾏其它线程，调⽤此⽅法，可以让线程执⾏更加均衡，但此⽅法提出的建议不⼀定会被采纳。此⽅法在单核CPU上⽐较明显，在多核CPU上，多个线程本⾝就是⽐较均衡的。

新建一个PrintNumberTask任务类：

public class PrintNumberTask implements Runnable{
    @Override
    public void run() {
        for (int i = 0; i < 10; i++) {
            IO.println(Thread.currentThread().getName() + ":" + i);

        }
    }
}

测试类：

public class Test01 {
    static void main() {
        PrintNumberTask pnt1 = new PrintNumberTask();
        for (int i = 0; i < 5; i++) {
            Thread.yield();//建议优先执行其他线程，多核效果不明显
            Thread t1 = new Thread(pnt1);
            t1.start();

        }
    }
}

(Thread).join()

让当前线程等待⽬标线程结束后再继续执⾏

public class Test02 {
    static void main() {
        Thread t1 = new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 1; i <= 3 ; i++) {
                    IO.println(i);
                }
            }
        });

        Thread t2 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    t1.join();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
                for (int i = 4; i <= 6 ; i++) {
                    IO.println(i);
                }
            }
        });

        Thread t3 = new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    t2.join();
                } catch (InterruptedException e) {
                    throw new RuntimeException(e);
                }
                for (int i = 7; i <= 9 ; i++) {
                    IO.println(i);
                }
            }
        });

        t1.start();
        t2.start();
        t3.start();
    }
}