题目：现在两个线程，可以操作同一个变量，实现一个线程对该变量加1，一个线程对该变量减1，实现交替，来10轮，变量初始值为零。

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

class ShareData {
    private int number = 0;
    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition();

    public void increment() throws Exception {
        lock.lock();
        try {
            while (number != 0) {
                condition.await();//this.wait();
            }
            ++number;
            System.out.println(Thread.currentThread().getName() + "\t" + number);
            condition.signalAll();//this.notifyAll();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }

    public void decrement() throws Exception {
        lock.lock();
        try {
            while (number == 0) {
                condition.await();//this.wait();
            }
            --number;
            System.out.println(Thread.currentThread().getName() + "\t" + number);
            condition.signalAll();//this.notifyAll();
        } catch (Exception e) {
            e.printStackTrace();
        } finally {
            lock.unlock();
        }
    }
//========这种写法是最原始的写法使用了synchronized========
/*  
    public synchronized void increment() throws Exception
    {
        while(number != 0)
        {
            this.wait();
        }
        ++number;
        System.out.println(Thread.currentThread().getName()+"\t"+number);
        this.notifyAll();
    }

    public synchronized void decrement() throws Exception
    {
        while(number == 0)
        {
            this.wait();
        }
        --number;
        System.out.println(Thread.currentThread().getName()+"\t"+number);
        this.notifyAll();
    }
    */
}

/**
 * 题目：现在两个线程，可以操作同一个变量，实现一个线程对该变量加1，一个线程对该变量减1，
 * 实现交替，来10轮，变量初始值为零。
 *
 * @author admin
 * 创建四个线程操作资源（高内聚，低耦合）
 */
public class ThreadDemo2 {
    public static void main(String[] args) {
        final ShareData sd = new ShareData();

        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 1; i <= 10; i++) {
                    try {
                        Thread.sleep(200);
                        sd.increment();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }, "AA").start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 1; i <= 10; i++) {
                    try {
                        Thread.sleep(300);
                        sd.decrement();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }, "BB").start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 1; i <= 10; i++) {
                    try {
                        Thread.sleep(400);
                        sd.increment();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }, "CC").start();

        new Thread(new Runnable() {
            @Override
            public void run() {
                for (int i = 1; i <= 10; i++) {
                    try {
                        Thread.sleep(500);
                        sd.decrement();
                    } catch (Exception e) {
                        e.printStackTrace();
                    }
                }
            }
        }, "DD").start();

    }
}

在这个需要注意一个问题在共享对象的方法里 将if替换为while，解决虚假唤醒的问题。