condition 线程间通讯

Condition是个接口，基本的方法就是await()和signal()方法；

Condition依赖于Lock接口，生成一个Condition的基本代码是lock.newCondition()
调用Condition的await()和signal()方法，都必须在lock保护之内，就是说必须在lock.lock()和lock.unlock之间才可以使用

Conditon中的await()对应Object的wait()；
Condition中的signal()对应Object的notify()；
Condition中的signalAll()对应Object的notifyAll()。

实例： 相对于 Object 中的方法 控制粒度 更细。

public class ThreeConditionCommunication {


    public static void main(String[] args) {
        Business bussiness = new Business();


        new Thread(new Runnable() {// 开启一个子线程


                    @Override
                    public void run() {
                        for (int i = 1; i <= 50; i++) {


                            bussiness.sub1(i);
                        }


                    }
                }).start();


        new Thread(new Runnable() {// 开启另一个子线程


            @Override
            public void run() {
                for (int i = 1; i <= 50; i++) {


                    bussiness.sub2(i);
                }


            }
        }).start();


        // main方法主线程
        for (int i = 1; i <= 50; i++) {


            bussiness.main(i);
        }
    }


    static class Business {


        Lock lock = new ReentrantLock();  //是一种 排他锁
        Condition condition1 = lock.newCondition(); //Condition是在具体的lock之上的
        Condition condition2 = lock.newCondition();
        Condition conditionMain = lock.newCondition();


        private int bShouldSub = 0;


        public void sub1(int i) {
            lock.lock();
            try {
                while (bShouldSub != 0) {
                    try {
                        condition1.await(); //用condition来调用await方法
                    } catch (Exception e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                for (int j = 1; j <= 10; j++) {
                    System.out.println("sub1 thread sequence of " + j
                            + ", loop of " + i);
                }
                bShouldSub = 1;
                condition2.signal(); //让线程2执行
            } finally {
                lock.unlock();
            }
        }


        public void sub2(int i) {
            lock.lock();
            try {
                while (bShouldSub != 1) {
                    try {
                        condition2.await(); //用condition来调用await方法
                    } catch (Exception e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                for (int j = 1; j <= 10; j++) {
                    System.out.println("sub2 thread sequence of " + j
                            + ", loop of " + i);
                }
                bShouldSub = 2;
                conditionMain.signal(); //让主线程执行
            } finally {
                lock.unlock();
            }
        }


        public void main(int i) {
            lock.lock();
            try {
                while (bShouldSub != 2) {
                    try {
                        conditionMain.await(); //用condition来调用await方法
                    } catch (Exception e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }
                for (int j = 1; j <= 5; j++) {
                    System.out.println("main thread sequence of " + j
                            + ", loop of " + i);
                }
                bShouldSub = 0;
                condition1.signal(); //让线程1执行
            } finally {
                lock.unlock();
            }
        }
    }
}