Java 多线程 （PART XIX） 使用Condition实现线程的顺序执行

join的实现

前面介绍了，如何使用jion方法实现线程的顺序执行。
http://blog.youkuaiyun.com/uncle_gy/article/details/78163215

condition的实现

package condition123;

import java.util.concurrent.locks.Condition;
import java.util.concurrent.locks.Lock;
import java.util.concurrent.locks.ReentrantLock;

public class Main {
    volatile private static int nextPrintWho = 1;
    volatile private static Lock lock = new ReentrantLock();
    final private static Condition condition= lock.newCondition();

    public static void main(String[] args) {
        Thread threadA = new Thread() {
            public void run() {
                try {
                    lock.lock();
                    while (nextPrintWho != 1) {
                        condition.await();
                    }
                    for (int i = 0; i < 3; i++) {
                        System.out.println("ThreadA " + (i + 1));
                    }
                    nextPrintWho = 2;
                    condition.signalAll();
                } catch (InterruptedException e) {

                } finally {
                    lock.unlock();
                }
            }
        };
        Thread threadB = new Thread() {
            public void run() {
                try {
                    lock.lock();
                    while (nextPrintWho != 2) {
                        condition.await();
                    }
                    for (int i = 0; i < 3; i++) {
                        System.out.println("ThreadB " + (i + 1));
                    }
                    nextPrintWho = 3;
                    condition.signalAll();
                } catch (InterruptedException e) {

                } finally {
                    lock.unlock();
                }
            }
        };
        Thread threadC = new Thread() {
            public void run() {
                try {
                    lock.lock();
                    while (nextPrintWho != 3) {
                        condition.await();
                    }
                    for (int i = 0; i < 3; i++) {
                        System.out.println("ThreadC " + (i + 1));
                    }
                    nextPrintWho = 1;
                    condition.signalAll();
                } catch (InterruptedException e) {

                } finally {
                    lock.unlock();
                }
            }
        };
        Thread[] aArray = new Thread[5];
        Thread[] bArray = new Thread[5];
        Thread[] cArray = new Thread[5];
        for (int i = 0; i < 5; i++) {
            aArray[i] = new Thread(threadA);
            bArray[i] = new Thread(threadB);
            cArray[i] = new Thread(threadC);
            aArray[i].start();
            bArray[i].start();
            cArray[i].start();
        }
    }

}

输出结果：

ThreadA 1
ThreadA 2
ThreadA 3
ThreadB 1
ThreadB 2
ThreadB 3
ThreadC 1
ThreadC 2
ThreadC 3
ThreadA 1
ThreadA 2
ThreadA 3
ThreadB 1
ThreadB 2
ThreadB 3
ThreadC 1
ThreadC 2
ThreadC 3
ThreadA 1
ThreadA 2
ThreadA 3
ThreadB 1
ThreadB 2
ThreadB 3
ThreadC 1
ThreadC 2
ThreadC 3
ThreadA 1
ThreadA 2
ThreadA 3
ThreadB 1
ThreadB 2
ThreadB 3
ThreadC 1
ThreadC 2
ThreadC 3
ThreadA 1
ThreadA 2
ThreadA 3
ThreadB 1
ThreadB 2
ThreadB 3
ThreadC 1
ThreadC 2
ThreadC 3

使用nextwhoPrint来控制下一个打印的线程是谁。每次使用condition.signalAll();来唤醒所有线程，每个线程都检查nextwhoPrint是不是自己的量，如果不是则再次condition.await();不过这里的ABC线程并不保证是同一个循环里的ABC，但是每个A和A之间是同步的。