多线程案例_循环打印_设计4个线程...

要求：设计4个线程，其中两个线程每次对 i 增加1，另外两个线程对 i 每次减少1，写出程序。

在以下程序中，numOfPrint 代表题目中的 i

为了解决本方唤醒其他一方的问题。可以一个锁创建多个监视器对象(Condition对象)。

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

/**
 * @author 馬建超 2018年1月19日 上午11:45:39
 */
public class ThreadTest6 {
    public static void main(String[] args) {
        final NumberIncreate ni = new NumberIncreate();
        new Thread(new Runnable() {

            @Override
            public void run() {
                for (int i = 0; i < 5; i++) {
                    ni.num();
                }

            }
        }, "A").start();
        new Thread(new Runnable() {

            @Override
            public void run() {
                for (int i = 0; i < 5; i++) {
                    ni.num2();
                }

            }
        }, "B").start();
        new Thread(new Runnable() {

            @Override
            public void run() {
                for (int i = 0; i < 5; i++) {
                    ni.num3();
                }

            }
        }, "C").start();
        new Thread(new Runnable() {

            @Override
            public void run() {
                for (int i = 0; i < 5; i++) {
                    ni.num4();
                }

            }
        }, "D").start();
    }

}

class NumberIncreate {
    private int num = 1;// 当前正在执行线程的标记
    private int numOfPrint = 0;// 打印的数字
    private Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition();
    Condition condition2 = lock.newCondition();
    Condition condition3 = lock.newCondition();
    Condition condition4 = lock.newCondition();

    public void num() {
        lock.lock();
        try {
            if (num != 1) {
                condition.await();
            }
            System.out.println("numOfPrint==" + numOfPrint++);
            num = 2;
            condition2.signal();
        } catch (Exception e) {
        } finally {
            lock.unlock();
        }

    }

    public void num2() {
        lock.lock();
        try {
            if (num != 2) {
                condition2.await();
            }
            System.out.println("numOfPrint==" + numOfPrint++);
            num = 3;
            condition3.signal();
        } catch (Exception e) {
        } finally {
            lock.unlock();
        }

    }

    public void num3() {
        lock.lock();
        try {
            if (num != 3) {
                condition3.await();
            }
            System.out.println("numOfPrint==" + numOfPrint--);
            num = 4;
            condition4.signal();
        } catch (Exception e) {
        } finally {
            lock.unlock();
        }

    }

    public void num4() {
        lock.lock();
        try {
            if (num != 4) {
                condition4.await();
            }
            System.out.println("numOfPrint==" + numOfPrint--);
            num = 1;
            condition.signal();
        } catch (Exception e) {
        } finally {
            lock.unlock();
        }

    }
}