线程间通信概述

线程间通信的模型有两种：共享内存和消息传递，以下方式都是基本这两种模型来实现的。

模拟场景---两个线程，一个线程对当前数值加 1，另一个线程对当前数值减 1,要求用线程间通信

synchronized 方案

//创建资源类，定义属性和操作方法
class Share{
    
    private int number = 0;
    
    //+1方法
    public synchronized void incr() throws InterruptedException {
        //二、判断 操作和通知
        while (number != 0) this.wait();//判断number值是否为0
        //如果number值为0
        number++;
        System.out.println(Thread.currentThread().getName()+"::"+number);
        //通知其他线程
        this.notifyAll();
    }
    //-1方法
    public synchronized void decr() throws InterruptedException {
        //判断
        while (number != 1) this.wait();
        //操作
        number--;
        System.out.println(Thread.currentThread().getName()+"::"+number);
        //通知其他线程
        this.notifyAll();
    }
}
public class ThreadDemo1 {
    //创建多个线程，调用资源类的操作方法
    public static void main(String[] args) {
        Share share = new Share();
        //创建线程
        new Thread(()->{
            for (int i = 1;i <= 10;i++){
                try {
                    share.incr(); //进行10次+1操作
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"线程一").start();

        new Thread(()->{
            for (int i = 1;i <= 10;i++){
                try {
                    share.decr(); //进行10次-1操作
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"线程二").start();
    }
}

Lock 方案

//第一步，创建资源类，定义属性和操作方法
class Share{
    private int number = 0;
    //创建lock
    private Lock lock = new ReentrantLock();
    private Condition condition = lock.newCondition();

    //+1
    public void incr() throws InterruptedException {
        //上锁
        lock.lock();
        try {
            //判断
            while (number != 0) condition.await();
            //操作
            number++;
            System.out.println(Thread.currentThread().getName()+"::"+number);
            //通知
            condition.signalAll();
        }finally {
            //解锁
            lock.unlock();
        }
    }

    //-1
    public void decr() throws InterruptedException {
        //上锁
        lock.lock();
        try {
            //判断
            while (number !=1) condition.await();
            //操作
            number--;
            System.out.println(Thread.currentThread().getName()+"::"+number);
            //通知
            condition.signalAll();
        }finally {
            //解锁
            lock.unlock();
        }
    }
}
public class ThreadDemo2 {
    public static void main(String[] args) {
        Share share = new Share();

        //创建多个线程
        new Thread(()->{
            for (int i=1;i<=10;i++){
                try {
                    share.incr();//进行10次+1操作
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"线程一").start();

        new Thread(()->{
            for (int i=1;i<=10;i++){
                try {
                    share.decr();//进行10次-1操作
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"线程二").start();
    }
}

线程间定制化通信

案例：线程一打印 5 次，线程二打印 10 次，线程三打印 15 次 ,按照此顺序循环 10 轮

//创建资源类，定义属性和操作方法
class ShareResource{
    //定义标志位
    private int flag = 1;
    //创建Lock锁
    private Lock lock = new ReentrantLock();

    //创建三个condition
    private Condition c1 = lock.newCondition();
    private Condition c2 = lock.newCondition();
    private Condition c3 = lock.newCondition();

    //打印5次,参数 第几轮
    public void print5(int loop) throws InterruptedException {
        //上锁
        lock.lock();
        try {
            //判断
            while (flag != 1){
                c1.await();
            }
            //操作 打印5次
            for (int i = 1;i <= 5;i++) System.out.println(Thread.currentThread().getName()+"::"+i+":轮数"+loop);
            //通知 先修改标志位为2 再通知第二个线程
            flag = 2;
            c2.signal();
        }finally {
            lock.unlock();
        }
    }
    public void print10(int loop) throws InterruptedException {
        //上锁
        lock.lock();
        try {
            //判断
            while (flag !=2){
                c2.await();
            }
            //操作 打印10次
            for (int i = 1; i <= 10; i++) System.out.println(Thread.currentThread().getName()+"::"+i+":轮数"+loop);
            flag = 3;
            //通知
            c3.signal();
        }finally {
            lock.unlock();
        }
    }

    public void print15(int loop) throws InterruptedException {
        //上锁
        lock.lock();
        try {
            //判断
            while (flag != 3){
                c3.await();
            }
            //操作 打印15次
            for (int i = 1; i <= 15; i++) System.out.println(Thread.currentThread().getName()+"::"+i+":轮数"+loop);
            flag = 1;
            //通知
            c1.signal();
        }finally {
            lock.unlock();
        }
    }
}
public class ThreadDemo3 {
    public static void main(String[] args) {
        ShareResource shareResource = new ShareResource();
        new Thread(()->{
            for (int i = 1; i <= 10; i++) {
                try {
                    shareResource.print5(i); //调用打印5次的方法
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"线程一").start();
        new Thread(()->{
            for (int i = 1; i <= 10; i++) {
                try {
                    shareResource.print10(i); //调用打印10次的方法
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"线程二").start();
        new Thread(()->{
            for (int i = 1; i <= 10; i++) {
                try {
                    shareResource.print15(i);//调用打印15次的方法
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"线程三").start();
    }
}