Concurrent - Phaser - forceTermination() & isTerminated()

原创转载请注明出处：http://agilestyle.iteye.com/blog/2344789

forceTermination()

forceTermination()的作用是使Phaser对象的屏障功能失效

isTerminated()

isTerminated()的作用是判断Phaser对象是否已经呈销毁状态

PhaserTest18.java

package org.fool.java.concurrent.phaser;

import java.util.concurrent.Phaser;

public class PhaserTest18 {
    public static class ThreadA implements Runnable {
        private Phaser phaser;

        public ThreadA(Phaser phaser) {
            this.phaser = phaser;
        }

        @Override
        public void run() {
            System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());

            phaser.arriveAndAwaitAdvance();

            System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
        }
    }

    public static class ThreadB implements Runnable {
        private Phaser phaser;

        public ThreadB(Phaser phaser) {
            this.phaser = phaser;
        }

        @Override
        public void run() {
            System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());

            phaser.arriveAndAwaitAdvance();

            System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
        }
    }

    public static void main(String[] args) {
        Phaser phaser = new Phaser(3);

        Thread t1 = new Thread(new ThreadA(phaser));
        t1.setName("ThreadA");
        t1.start();

        Thread t2 = new Thread(new ThreadB(phaser));
        t2.setName("ThreadB");
        t2.start();
    }
}

Run

Note:

ThreadA和ThreadB呈阻塞状态，因为计数未达到3

修改main方法

public static void main(String[] args) {
	try {
		Phaser phaser = new Phaser(3);

		Thread t1 = new Thread(new ThreadA(phaser));
		t1.setName("ThreadA");
		t1.start();

		Thread t2 = new Thread(new ThreadB(phaser));
		t2.setName("ThreadB");
		t2.start();

		Thread.sleep(1000);

		phaser.forceTermination();

		System.out.println(phaser.isTerminated());
	} catch (InterruptedException e) {
		e.printStackTrace();
	}
}

再Run

Note:

forceTermination()仅仅将屏障取消，线程继续执行后面的代码，并不出现异常，而CyclicBarrier的reset()方法执行时会出现异常。

控制Phaser类的运行时机

控制线程一起到达屏障后不允许继续运行

PhaserTest20.java

package org.fool.java.concurrent.phaser;

import java.util.concurrent.Phaser;

public class PhaserTest20 {
    public static class MyThread implements Runnable {
        private Phaser phaser;

        public MyThread(Phaser phaser) {
            this.phaser = phaser;
        }

        @Override
        public void run() {
            System.out.println(Thread.currentThread().getName() + " A1 begin " + System.currentTimeMillis());

            phaser.arriveAndAwaitAdvance();

            System.out.println(Thread.currentThread().getName() + " A1 end " + System.currentTimeMillis());
        }
    }

    public static void main(String[] args) {
        try {
            Phaser phaser = new Phaser(3);
            System.out.println(phaser.getRegisteredParties());

            phaser.register();

            System.out.println(phaser.getRegisteredParties());

            for (int i = 0; i < 3; i++) {
                Thread t = new Thread(new MyThread(phaser));
                t.start();
            }

            Thread.sleep(5000);
            System.out.println("wait for 5 seconds...");
            phaser.arriveAndDeregister();
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
    }
}

Run

Note:

本例说明Phaser类运行的时机是可以逻辑控制的，主要的原理就是计数+1，然后通过逻辑代码的方式来决定线程是否继续向下运行。 

Reference

Java并发编程核心方法与框架