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java锁:第二章:可重入锁和递归锁

笙烛 2022-05-16 阅读 40


可重入锁是什么?

java锁:第二章:可重入锁和递归锁_发短信

可以防止死锁,是同一把锁

代码:

package com.javaliao.backstage;

class Phone{

public synchronized void sendSMS(){
System.out.println(Thread.currentThread().getName()+"\t 发短信");
sendEmail();
}
public synchronized void sendEmail(){
System.out.println(Thread.currentThread().getName()+"\t 发邮件");
}
}
public class Demo {
public static void main(String[] args) {
Phone phone = new Phone();
new Thread(()->{
phone.sendSMS();
},"t1").start();
new Thread(()->{
phone.sendSMS();
},"t2").start();
}
}

控制台:

java锁:第二章:可重入锁和递归锁_发短信_02

生活案例:

家里的大门有一把锁,厕所没有上锁。我进了大门了,就不用在厕所上锁了。

ReentrantLock就是把可重入锁

package com.javaliao.backstage;


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

class Phone implements Runnable{

Lock lock = new ReentrantLock();
@Override
public void run() {
sendSMS();
}

public void sendSMS(){
//加几把就要解锁几次
lock.lock();
lock.lock();
try {
System.out.println(Thread.currentThread().getName()+"\t 发短信");
sendEmail();
} finally {
lock.unlock();
lock.unlock();
}
}
public void sendEmail(){
lock.lock();
try {
System.out.println(Thread.currentThread().getName()+"\t 发邮件");
} finally {
lock.unlock();
}
}


}
public class Demo {
public static void main(String[] args) {
Phone phone = new Phone();
Thread t1 = new Thread(phone,"t1");
Thread t2 = new Thread(phone,"t2");
t1.start();
t2.start();
}
}

java锁:第二章:可重入锁和递归锁_java_03








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