02-生产者消费者问题&condition 实现精准唤醒

package test01;


public class PC {
    public static void main(String[] args) {
        Data data = new Data();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"A").start();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"B").start();
    }
}
//等待 业务 通知
class Data{
    private int number =0;
    //+1
    public synchronized void increment() throws InterruptedException {
        if(number!=0){
            //等待
            this.wait();
        }
        number++;
        System.out.println(Thread.currentThread().getName()+"=="+number);
        //通知
        this.notifyAll();
    }
    //-1
    public synchronized void decrement() throws InterruptedException {
        if(number==0){
            this.wait();
        }
        number--;
        System.out.println(Thread.currentThread().getName()+"=="+number);

        //通知
        this.notifyAll();
    }
}

问题 ： 如果4个线程呢？ A B C D 虚假唤醒

if 改为 while 就行了

  while(number!=0){
            //等待
            this.wait();
        }
        number++;
        System.out.println(Thread.currentThread().getName()+"=="+number);
        //通知
        this.notifyAll();

代码实现

package test01;

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

public class PC2 {
    public static void main(String[] args) {
        Data2 data2 = new Data2();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data2.increment();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"A").start();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data2.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"B").start();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data2.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"C").start();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                try {
                    data2.decrement();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        },"D").start();
    }
}

//等待 业务 通知
class Data2{
    private int number =0;
    Lock lock=new ReentrantLock();
    Condition condition=lock.newCondition();

    //    condition.await(); //等待
    //    condition.signalAll(); //唤醒
    public  void increment() throws InterruptedException {
      lock.lock();
        try {
          while(number!=0){
              condition.await();
          }
          number++;
          System.out.println(Thread.currentThread().getName()+"=="+number);
          condition.signalAll();
      }catch (Exception e){
          e.printStackTrace();
      }finally {
          lock.unlock();
      }

    }
    public  void decrement() throws InterruptedException {
       lock.lock();
       try{
           while(number==0){
               condition.await();
           }
           number--;
           System.out.println(Thread.currentThread().getName()+"=="+number);
           condition.signalAll();
       }catch (Exception e){
           e.printStackTrace();
       }finally {
           lock.unlock();
       }
    }
}

任何一个新的技术，绝对不是仅仅只是覆盖了原来的技术， 优势和补充

package test01;

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

public class PC3 {
    public static void main(String[] args) {
        Data3 data3 = new Data3();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                data3.printA();
            }
        },"A").start();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                data3.printB();
            }
        },"B").start();
        new Thread(()->{
            for (int i = 0; i < 10; i++) {
                data3.printC();
            }
        },"C").start();
    }
}
class Data3{
    private Lock lock=new ReentrantLock();
    private Condition condition1=lock.newCondition();
    private Condition condition2=lock.newCondition();
    private Condition condition3=lock.newCondition();
    private int number=1;//1A 2B 3C

    public void printA(){
        lock.lock();
        try{//业务
        while (number!=1){
            condition1.await();
        }
            System.out.println(Thread.currentThread().getName()+"===>AAAA");
            //唤醒 唤醒指定B
            number=2;
            condition2.signal();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }
    public void printB(){
        lock.lock();
        try{
            while (number!=2){
                condition2.await();
            }
            System.out.println(Thread.currentThread().getName()+"===>BBBB");
        number=3;
        condition3.signal();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }
    public void printC(){
        lock.lock();
        try{
            while (number!=3){
                condition3.await();
            }
            System.out.println(Thread.currentThread().getName()+"===>CCCC");
            number=1;
            condition1.signal();
        }catch (Exception e){
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }
}