可重入锁是什么？
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：
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(); } }
