Java使用Condition实现精准唤醒线程详解

package testJUC;

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

public class TestCondition {
    public static void main(String[] args) {
        Product3 product = new Product3();
        new Thread(()->{
            for (int i = 0; i < 5; i++)
                new Producer(product).getProduct();

        },"工厂").start();

        new Thread(()->{
            for (int i = 0; i < 5; i++)
                new Consumer(product).saleProduct();
        },"学生").start();
    }
}

class Product3 {
    private Lock lock = new ReentrantLock();
    private Condition condition1 = lock.newCondition();
    private Condition condition2 = lock.newCondition();
    private int flag = 1;//标识符

    public void getProduct() {
        //加锁
        lock.lock();
        try {
        //使用while循环，可以有效避免线程虚假唤醒
            while (flag != 1) {
                condition1.await();
            }
            flag = 2;
            //唤醒saleProduct
            condition2.signal();
            System.out.println(Thread.currentThread().getName() + "生产一个产品");
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            //解锁
            lock.unlock();
        }
    }



    public void saleProduct() {
        lock.lock();
        try {
            while (flag != 2) {
                condition2.await();
            }
            flag = 1;
            //唤醒getProduct
            condition1.signal();
            System.out.println(Thread.currentThread().getName()+"消费了一个产品");
        }catch (InterruptedException e) {
            e.printStackTrace();
        }finally {
            lock.unlock();
        }
    }
}
//实体类
class Producer{
    private Product3 product = null;
    public Producer(Product3 product) {
        this.product = product;
    }
    public void getProduct(){
        product.getProduct();
    }
}

class Consumer{
    private Product3 product = null;

    public Consumer(Product3 product) {
        this.product = product;
    }

    public void saleProduct(){
        product.saleProduct();
    }
}

package testJUC;

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

public class TestCondition {
    public static void main(String[] args) {
        Print print = new Print();
        new Thread(() -> {
            for (int i = 0; i < 5; i++)
                print.printA();
        }).start();
        new Thread(() -> {
            for (int i = 0; i < 5; i++)
                print.printB();
        }).start();
        new Thread(() -> {
            for (int i = 0; i < 5; i++)
                print.printC();
        }).start();

    }
}


class Print {
    private Lock lock = new ReentrantLock();
    private Condition condition1 = lock.newCondition();
    private Condition condition2 = lock.newCondition();
    private Condition condition3 = lock.newCondition();
    private int number = 1;

    //输出A的方法
    public void printA() {
        //加锁
        lock.lock();
        try {
            //使用while循环，可以有效避免线程虚假唤醒
            while (number != 1) {
                condition1.await();
            }
            number = 2;
            //唤醒输出B的方法
            condition2.signal();
            System.out.println("AAA");
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            //解锁
            lock.unlock();
        }

    }

    //输出B的方法
    public void printB() {
        //加锁
        lock.lock();
        try {
            while (number != 2) {
                condition2.await();
            }
            System.out.println("BBB");
            number = 3;
            //唤醒C
            condition3.signal();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            //唤醒输出C的方法
            lock.unlock();
        }
    }

    //输出C的方法
    public void printC() {
        //加锁
        lock.lock();
        try {
            while (number != 3) {
                condition3.await();
            }
            System.out.println("CCC");
            number = 1;
            //唤醒输出A的方法
            condition1.signal();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            //解锁
            lock.unlock();
        }
    }
}