Detailed explanation of Java multithreaded communication implementation

This article mainly introduces the detailed implementation of Java multi-threaded communication. The example code is introduced in great detail, which has a certain reference value for everyone's study or work. Friends in need can refer to it

Thread communication mode:

1. Shared variable

Inter thread communication can send signals. A simple way to send signals is to set the signal value in the variable of the shared object. Thread a sets the Boolean member variable hasdatatoprocess to true in a synchronization block, and thread B also reads the member variable hasdatatoprocess in the synchronization code block. This simple example uses an object that holds a signal and provides set and get methods.

public class MySignal1 {
  //共享的变量
  private boolean hasDataToProcess = false;

  //取值
  public boolean getHasDataProcess() {
    return hasDataToProcess;
  }

  //存值
  public void setHasDataToProcess(boolean hasDataToProcess) {
    this.hasDataToProcess = hasDataToProcess;
  }

  public static void main(String[] args) {
    //同一个对象
    final MySignal1 my = new MySignal1();
    //线程1设置hasDataToProcess值为true
    final Thread t1 = new Thread(new Runnable() {
      @Override
      public void run() {
        my.setHasDataToProcess(true);
      }
    });
    t1.start();
    //线程2取这个值hasDataToProcess
    Thread t2 = new Thread(new Runnable() {
      @Override
      public void run() {
        try {
          //等待线程1完成后取值
          t1.join();
        } catch (InterruptedException e) {
          e.printStackTrace();
        }
        my.getHasDataProcess();
        System.out.println("t1改变以后的值："+my.getHasDataProcess());
      }
    });
    t2.start();
  }
}

The operation results are as follows:

Value after T1 change: true

2. Wait / notify mechanism

Taking resources as an example, a producer produces a resource and informs consumers to consume a resource. The producer continues to produce resources and consumers consume resources. This cycle is coded as follows.

import sun.security.util.Password;

//资源类
class Resource {
  private String name;
  private int count = 1;
  private boolean flag = false;

  public synchronized void set(String name) {
    //生产资源
    while (flag) {
      try {
        //线程等待
        wait();
      } catch (InterruptedException e) {
      }
    }
    this.name = name + "----" + count + "+++++";
    System.out.println(Thread.currentThread().getName() + "..生产者..." + this.name);
    flag = true;
    //唤醒等待中的消费者
    this.notifyAll();
  }

  public synchronized void out() {
    //消费资源
    while (!flag) {
      try {
        //线程等待，生产者生产资源
        wait();
      } catch (InterruptedException e) {
      }
    }
    System.out.println(Thread.currentThread().getName() + "...消费者..." + this.name);
    flag = false;
    //唤醒消费者，生产资源
    this.notifyAll();
  }
}

//生产者
class Producer implements Runnable {
  private Resource rs;

  public Producer(Resource rs) {
    this.rs = rs;
  }

  //生产者生产资源
  @Override
  public void run() {
    while (true) {
      rs.set("商品");
    }
  }
}

//消费者消费资源
class Consumer implements Runnable {
  private Resource rs;

  public Consumer(Resource rs) {
    this.rs = rs;
  }

  //消费者消费资源
  @Override
  public void run() {
    while (true) {
      rs.out();
    }
  }
}

public class ProducerConsumerDemo {
  public static void main(String[] args) {
    Resource r = new Resource();
    Producer p = new Producer(r);
    Consumer c = new Consumer(r);
    Thread t1 = new Thread(p);
    Thread t2 = new Thread(c);
    t1.start();
    t2.start();
  }
}

The operation results are as follows:

Thread-0..生产者...商品----1+++++
Thread-1...消费者...商品----1+++++
Thread-0..生产者...商品----1+++++
Thread-1...消费者...商品----1+++++
Thread-0..生产者...商品----1+++++
Thread-1...消费者...商品----1+++++
Thread-0..生产者...商品----1+++++

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