java - Java：ReentrantLock 不起作用它仍然相互混合

Question

我无法弄清楚为什么代码不能正常工作。线程仍然相互混合。

我有 A 类：

package com.company;

public class A implements Runnable {
    ReentrantLockClass r;

    public A(ReentrantLockClass r) {
        this.r = r;
    }

    @Override
    public void run() {
        r.print(5);
    }
}

和 B 类：

package com.company;

public class B implements Runnable{
    ReentrantLockClass r;

    public B(ReentrantLockClass r) {
        this.r = r;
    }

    @Override
    public void run() {
        r.print(10);
    }
}

这是用于运行 ReentrantLock 的 ReentrantLockClass

package com.company;

import java.util.concurrent.locks.ReentrantLock;

public class ReentrantLockClass {
    public void print(int count){
        ReentrantLock lock = new ReentrantLock();
        try {
            lock.lock();
            for(int i = 1 ; i <= 10 ; i ++){
                System.out.println(count * i);
                Thread.sleep(500);
            }
        }
        catch (Exception e){}
        finally {
           lock.unlock();
        }
    }
}

这是主要课程：

package com.company;

public class Main {

    public static void main(String[] args) {
        ReentrantLockClass r = new ReentrantLockClass();

        A a = new A(r);
        B b = new B(r);

        Thread t1 = new Thread(a);
        Thread t2 = new Thread(b);

        t1.start();
        t2.start();
    }
}

这是输出：

它应该运行一个线程然后运行其他线程

标签： javamultithreadingooplockingreentrantlock

Answer 1

该print方法创建一个新ReentrantLock实例。因此，每个线程锁定自己的锁，因此它们不会相互阻塞。一种方法是在ReentrantLockClass' （隐式）构造函数中创建锁，然后在print方法中将其锁定：

public class ReentrantLockClass {
    // One lock shared for the instance
    ReentrantLock lock = new ReentrantLock();

    public void print(int count){
        try {
            lock.lock();
            for(int i = 1 ; i <= 10 ; i ++){
                System.out.println(count * i);
                Thread.sleep(500);
            }
        }
        catch (Exception e){}
        finally {
           lock.unlock();
        }
    }
}