锁/消费者问题/多线程

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原创最新推荐文章于 2026-05-22 09:32:28 发布 222 阅读 AI 写同款· GEO 优化 ›

Java多线程高级控制：条件对象和锁对象的实战演示在Java中，Object类的waitnotify和notifyAll方法是用于线程间通信的基础机制。它们允许一个线程在等待某个条件成立时放弃CPU的控制权，而其他线程在条件成立时通过notify或notifyAll方法来唤醒这些等待的线程。然而，这种方式存在一些局限性，如无法区分不同条件的等待与通知，以及在唤醒等待线程时没有优先级区分等。Condition接口在包中提供了一种更加灵活的机制，它允许线程在满足一个或多个条件的前提下进入等待状态。与Object。阅读详情

引言：

1.Synchronized：配合wait()、notifyAll()；

2.Lock：配合await()、signalAll()；

（1）用Synchronized来实现多个线程(四个)对共享资源ticket进行加、减操作；

始终在0 ， 1数值两个之间进行切换。

package com.tencent.JUC;

public class Lock {
    public static void main(String[] args) throws Exception {
        Ticket t = new Ticket();
        //四个线程
        new Thread( ()->{
            for(int i=0;i<10;i++) {
                try {
                    t.incre();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        } , "A").start();

        new Thread( ()->{
            for(int i=0;i<10;i++) {
                    try {
                        t.decre();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
            }
        } , "B").start();

        new Thread( ()->{
            for(int i=0;i<10;i++) {
                try {
                    t.incre();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        } , "C").start();

        new Thread( ()->{
            for(int i=0;i<10;i++) {
                try {
                    t.decre();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        } , "D").start();
    }
}

class Ticket {
    private static int number = 0;

    public synchronized void incre() throws InterruptedException {
        while(number != 0) {   //循环:解决虚拟唤醒的问题
            this.wait();
        }
        System.out.println(Thread.currentThread().getName() + "线程:" + number + "准备+1");
        number++;
        this.notifyAll();  //唤醒除自己之外的其它几个等待线程
    }

    public synchronized void decre() throws InterruptedException {
        while(number == 0) {
            this.wait();
        }
        System.out.println(Thread.currentThread().getName() + "线程:"  + number + "准备-1");
        number--;
        this.notifyAll();
    }
}

（2）同上，改为用Lock锁来实现生产者、消费者问题：

package com.tencent.JUC;


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

public class LockTest {
    public static void main(String[] args) throws Exception {
        Ticket2 t = new Ticket2();
        //四个线程
        new Thread( ()->{
            for(int i=0;i<10;i++) {
                try {
                    t.incre();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        } , "A").start();

        new Thread( ()->{
            for(int i=0;i<10;i++) {
                    try {
                        t.decre();
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
            }
        } , "B").start();

        new Thread( ()->{
            for(int i=0;i<10;i++) {
                try {
                    t.incre();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        } , "C").start();

        new Thread( ()->{
            for(int i=0;i<10;i++) {
                try {
                    t.decre();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        } , "D").start();
    }
}

class Ticket {
        private static int number = 0;

    public synchronized void incre() throws InterruptedException {
        while(number != 0) {   //循环:解决虚拟唤醒的问题
            this.wait();
        }
        System.out.println(Thread.currentThread().getName() + "线程:" + number + "准备+1");
        number++;
        this.notifyAll();  //唤醒除自己之外的其它几个等待线程
    }

    public synchronized void decre() throws InterruptedException {
        while(number == 0) {
            this.wait();
        }
        System.out.println(Thread.currentThread().getName() + "线程:"  + number + "准备-1");
        number--;
        this.notifyAll();
    }
}

class Ticket2 {
    private static int number = 0;

    Lock lock = new ReentrantLock();
    Condition condition = lock.newCondition(); //锁的监视器

    public void incre() throws InterruptedException {
        try {
            lock.lock();
            //业务代码
            while(number != 0) {
                condition.await();
            }
            System.out.println(Thread.currentThread().getName() + "线程:"  + number + "准备+1");
            number++;
            condition.signalAll();
        } catch (Exception e ) {
            System.out.println(e.getMessage());
        } finally {
            lock.unlock();
        }
    }

    public void decre() throws InterruptedException {
        try {
            lock.lock();
            //业务代码
            while(number == 0) {
                condition.await();
            }
            System.out.println(Thread.currentThread().getName() + "线程:"  + number + "准备-1");
            number--;
            condition.signalAll();
        } catch (Exception e ) {
            System.out.println(e.getMessage());
        } finally {
            lock.unlock();
        }
    }
}

（3）测试：

"C:\Program Files\Java\jdk1.8.0_101\bin\java.exe" "-javaagent:D:\IntelliJ IDEA 2020.1.2\lib\idea_rt.jar=59384:D:\IntelliJ IDEA 2020.1.2\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_101\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_101\jre\lib\rt.jar;F:\test-0517-tencent\out\production\test-0517-tencent;F:\test-0517-tencent\src\lib\commons-io-1.4.jar" com.tencent.JUC.LockTest
A线程:0准备+1
B线程:1准备-1
C线程:0准备+1
B线程:1准备-1
A线程:0准备+1
B线程:1准备-1
A线程:0准备+1
B线程:1准备-1
A线程:0准备+1
B线程:1准备-1
A线程:0准备+1
B线程:1准备-1
A线程:0准备+1
B线程:1准备-1
A线程:0准备+1
B线程:1准备-1
A线程:0准备+1
B线程:1准备-1
A线程:0准备+1
B线程:1准备-1
A线程:0准备+1
D线程:1准备-1
C线程:0准备+1
D线程:1准备-1
C线程:0准备+1
D线程:1准备-1
C线程:0准备+1
D线程:1准备-1
C线程:0准备+1
D线程:1准备-1
C线程:0准备+1
D线程:1准备-1
C线程:0准备+1
D线程:1准备-1
C线程:0准备+1
D线程:1准备-1
C线程:0准备+1
D线程:1准备-1
C线程:0准备+1
D线程:1准备-1

Process finished with exit code 0

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