Java Thread join() 的用法

        Java Thread中， join() 方法主要是让调用该方法的thread完成run方法里面的东西后，再执行join()方法后面的代码。示例：

package com.bijian.study;

class ThreadTesterA implements Runnable {

    private int counter;

    @Override
    public void run() {
        while (counter <= 10) {
            System.out.print("Counter = " + counter + " ");
            counter++;
        }
        System.out.println();
    }
}

class ThreadTesterB implements Runnable {

    private int i;

    @Override
    public void run() {
        while (i <= 10) {
            System.out.print("i = " + i + " ");
            i++;
        }
        System.out.println();
    }
}

public class ThreadTester {
    public static void main(String[] args) throws InterruptedException {
        Thread t1 = new Thread(new ThreadTesterA());
        Thread t2 = new Thread(new ThreadTesterB());
        t1.start();
        t1.join(); // wait t1 to be finished
        t2.start();
        t2.join(); // in this program, this may be removed
    }
}

运行结果：

Counter = 0 Counter = 1 Counter = 2 Counter = 3 Counter = 4 Counter = 5 Counter = 6 Counter = 7 Counter = 8 Counter = 9 Counter = 10 
i = 0 i = 1 i = 2 i = 3 i = 4 i = 5 i = 6 i = 7 i = 8 i = 9 i = 10

        如果去掉t1.join()这个语句过后， 输出的书序是乱的， 如下所示：

Counter = 0 Counter = 1 i = 0 Counter = 2 i = 1 Counter = 3 i = 2 Counter = 4 i = 3 Counter = 5 i = 4 Counter = 6 i = 5 Counter = 7 i = 6 Counter = 8 i = 7 Counter = 9 i = 8 Counter = 10 i = 9 
i = 10 

        加上这个语句过后， 就会按照顺序输出，从某种意义上说实现了同步。