【详解】Java多线程之线程间的通讯

案例一：消费者生产者模型（notify，wait）

public class ProduceConsumerV1 {
    private final Object LOCK = new Object();
    private int i = 0;//资源

    private boolean isProducted = false;//是否生产

    public void consumer(){
        synchronized (LOCK){
            if(isProducted){//已生产
                System.out.println("C->" + i);
                isProducted = false;
                LOCK.notify();//唤醒等待的生产者
            }else {//未生产
                try {
                    LOCK.wait();//等待生产
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
    }

    public void producter(){

        synchronized (LOCK){

            if (isProducted){//已生产
                try {
                    LOCK.wait();//等待消费
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }else{//未生产
                i++;
                System.out.println("P->" + i);
                isProducted = true;
                LOCK.notify();//唤醒等待的消费者
            }
        }

    }

    public static void main(String[] args) {
        ProduceConsumerV1 v1 = new ProduceConsumerV1();
        
        new Thread(()->{
            while (true){
                v1.consumer();
            }
            
        }).start();

        new Thread(()->{
            while (true){
                v1.producter();
            }

        }).start();
    }

}

案例二：多线程工作时对线程数目的控制

需求：

启动多个线程完成采集任务
线程数目越多，反而可能会影响性能，所以需要控制正在工作的线程数目，控制在最多三个线程工作

public class CaptureService {

    final static private LinkedList<Control> CONTROLS = new LinkedList<>();

    public static void main(String[] args) {

        List<Thread> works = new ArrayList<>();

        Arrays.asList("M1","M2","M3","M4","M5","M6","M7","M8","M9","M10").stream()
        .map(CaptureService::creatCaptureThread)
        .forEach(t->{
            t.start();
            works.add(t);
        });
        works.forEach(t->{
            try {
                t.join();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        });

        System.out.println("所有的采集已经完成！！！");
    }



    private static Thread creatCaptureThread(String name){

        return new Thread(()->{
            System.out.println("采集者[" + Thread.currentThread().getName() + "]准备采集数据");
            synchronized (CONTROLS){//判断工作的线程是否超过3个
                while (CONTROLS.size()>=3){
                    try {
                        CONTROLS.wait();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
                CONTROLS.addLast(new Control());//当工作的线程的不到3个时，加入到工作队列
            }

            System.out.println("采集者[" + Thread.currentThread().getName() + "]开始采集数据");

            try {
                Thread.sleep(10_000);
            } catch (InterruptedException e) {
                e.printStackTrace();
            }

            synchronized (CONTROLS){//完成工作，唤醒其他线程，同时退出工作队列
                System.out.println("采集者[" + Thread.currentThread().getName() + "]完成采集数据");
                CONTROLS.notifyAll();
                CONTROLS.removeFirst();
            }
        },name);

    }

    private static class Control{


    }
}