Java中join和yield的作用
1、 A.join,在API中的解释是,堵塞当前线程B,直到A执行完毕并死掉,再执行B。
用一个小例子来说明吧
static class ThreadA extends Thread { @Override public void run() { // TODO Auto-generated method stub super.run(); for (int i = 0; i < 10; i++) { System.out.println("ThreadA" + i); } } } static class ThreadB extends Thread { ThreadA a; public ThreadB(ThreadA a) { // TODO Auto-generated constructor stub this.a = a; } @Override public void run() { // TODO Auto-generated method stub super.run(); System.out.println("ThreadB start"); try { a.join(); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("ThreadB end"); } } public static void main(String[] args) { ThreadA a = new ThreadA(); ThreadB b = new ThreadB(a); b.start(); a.start(); }
程序的运行结果是:
ThreadB start
ThreadA0
ThreadA1
ThreadA2
ThreadA3
ThreadA4
ThreadA5
ThreadA6
ThreadA7
ThreadA8
ThreadA9
ThreadB end
首先b线程执行,a线程join后,直接执行完a,然后才执行b,证实上述说法。
2、A.yield,A让出位置,给B执行,B执行结束A再执行。跟join意思正好相反!
static class ThreadA extends Thread { @Override public void run() { // TODO Auto-generated method stub super.run(); for (int i = 0; i < 10; i++) { System.out.println("ThreadA " + i); } } } static class ThreadB extends Thread { ThreadA a; public ThreadB(ThreadA a) { // TODO Auto-generated constructor stub this.a = a; } @Override public void run() { // TODO Auto-generated method stub super.run(); System.out.println("ThreadB start"); try { for (int i = 0; i < 10; i++) { if(i==2){ a.yield(); } System.out.println("ThreadB " + i); } } catch (Exception e) { // TODO Auto-generated catch block e.printStackTrace(); } System.out.println("ThreadB end"); } } public static void main(String[] args) { ThreadA a = new ThreadA(); ThreadB b = new ThreadB(a); b.start(); a.start(); }
ThreadB start
ThreadA 0
ThreadB 0
ThreadA 1
ThreadB 1
ThreadA 2
ThreadB 2
ThreadB 3
ThreadB 4
ThreadB 5
ThreadB 6
ThreadB 7
ThreadB 8
ThreadB 9
ThreadB end
ThreadA 3
ThreadA 4
ThreadA 5
ThreadA 6
ThreadA 7
ThreadA 8
ThreadA 9
首先B执行,然后A执行;在B的循环中,i=2时,A执行yield;接着B执行完,才轮到A执行。
posted on 2017-07-30 22:39 luzhouxiaoshuai 阅读(291) 评论(0) 编辑 收藏 举报