我的Producer - Consumer代码陷入死锁

Question

代码正在进入死锁。即使它在命中wait()时立即进入生产者部分，它也会陷入死锁。据我所知，如果wait()被击中，它应该转到消费者线程，而不是进入死锁。

package com.java.thread.self.practice;

public class Producer_Consumer {

        private volatile boolean prodFlag = true;
        private volatile boolean consFlag = false;

        public static void main(String[] args){

            Producer_Consumer producer_Consumer = new Producer_Consumer();
            producer_Consumer.startThreads();

        }

        private void startThreads() {

            Thread producer = new Thread(new Runnable(){

                @Override
                public void run() {
                    while(true){
                        try {
                            System.out.println("Before Producer invocation :::::: ");
                            producer();
                            Thread.sleep(100);
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }

                }

            });



            Thread consumer = new Thread(new Runnable(){

                @Override
                public void run() {
                    while(true){
                        try {
                            System.out.println("Before Consumer invocation :::::: ");
                            consumer();
                            Thread.sleep(100);
                        } catch (InterruptedException e) {
                            // TODO Auto-generated catch block
                            e.printStackTrace();
                        }
                    }
                }

            });


            producer.start();
            consumer.start();
        }

         void producer() throws InterruptedException {

             System.out.println("Inside the producer method ::::: "+this.getClass());

             synchronized(this){

                 if(prodFlag){

                     System.out.println("PRODUCE !!!");
                     consFlag = true;
                     System.out.println("Before calling wait in producer :::::: ");
                     notify();
                     wait();
                     System.out.println("After calling wait in producer :::::: ");

                 }else{

                     System.out.println("Before calling notify in producer :::::: ");
                     consFlag = true;
                     wait();
                     System.out.println("After calling notify in producer :::::: ");

                 }


             }
        }

         void consumer() throws InterruptedException {

             System.out.println("Inside the consumer method ::::: "+this.getClass());

             synchronized(this){

                 if(consFlag){

                     System.out.println("CONSUME !!!");
                     prodFlag = true;
                     System.out.println("Before calling wait in consumer :::::: ");
                     notify();
                     wait();
                     System.out.println("After calling wait in consumer :::::: ");

                 }else{

                     System.out.println("Before calling notify in consumer :::::: ");
                     prodFlag = true;

                     wait();

                     System.out.println("After calling wait in consumer :::::: ");

                 }

             }
        }
}

Answer 1

当你这样做的时候

synchronized(this)

你锁定了整个类。它将被锁定，直到该代码块的末尾。由于您将标志声明为volatile，因此不需要显式同步。

在这种情况下，您根本不需要向wait()和notify发送信号。但是，如果您希望拥有一些原子业务逻辑，则需要重新编写代码，以避免将类作为键阻塞整个大块。

Answer 2

您的程序不会进入死锁-无论是在运行时，还是在调试时。我想您不熟悉调试多个线程，对吧？也许在您看来，您的生产线程处于死锁状态，而您必须切换到消耗线程并继续调试？