Java并发编程五公平锁和重入锁ReentrantLock与synchronized

Z时代
2024-01-10
分类：综合

1.重入锁ReentrantLock与synchronized的区别

synchronized 与重入锁是一样的，新旧线程一直可以一起竞争锁。

1.synchronized属于java关键字，

2.synchronized能对方法，代码块，对象进行加锁。

3.ReentrantLock需要执行lock()上锁unlock()解锁。

public class Test {
//true 为公平锁，false为重入锁
public   static         ReentrantLock lock = new ReentrantLock(false);
    public static void main(String [] args) throws InterruptedException {
        ThreadJoinTest t1 = new ThreadJoinTest("李雷");
ThreadJoinTest t2 = new ThreadJoinTest("韩梅梅");
ThreadJoinTest t3 = new ThreadJoinTest("露西");
ThreadJoinTest t4 = new ThreadJoinTest("莉莉");
t1.start();
t2.start();
t3.start();
t4.start();
System.out.println("Main thread is finished");
}
}
class ThreadJoinTest extends Thread{
public ThreadJoinTest(String name){
super(name);
}
@Override
public void  run(){
        Test.lock.lock();
          for(int i=0;i<3;i++){
              System.out.println(this.getName() + ":" + DateUtil.formatTime(new Date()));
ThreadUtil.sleep(1000);
}
        Test.lock.unlock();
}
}

执行结果线程随机执行

Main thread is finished
露西:15:12:28
露西:15:12:29
露西:15:12:30
莉莉:15:12:31
莉莉:15:12:32
莉莉:15:12:33
韩梅梅:15:12:34
韩梅梅:15:12:35
韩梅梅:15:12:36
李雷:15:12:37
李雷:15:12:38
李雷:15:12:39

synchronized 的结果是一样的

2.公平锁

公平锁可以理解为线程池的newSingleThreadExecutor,锁先到先得

public class Test {
//true 为公平锁，false为重入锁
public   static         ReentrantLock lock = new ReentrantLock(true);
    public static void main(String [] args) throws InterruptedException {
        ThreadJoinTest t1 = new ThreadJoinTest("李雷");
ThreadJoinTest t2 = new ThreadJoinTest("韩梅梅");
ThreadJoinTest t3 = new ThreadJoinTest("露西");
ThreadJoinTest t4 = new ThreadJoinTest("莉莉");
t1.start();
t2.start();
t3.start();
t4.start();
System.out.println("Main thread is finished");
}
}
class ThreadJoinTest extends Thread{
public ThreadJoinTest(String name){
super(name);
}
@Override
public void  run(){
        Test.lock.lock();
          for(int i=0;i<3;i++){
              System.out.println(this.getName() + ":" + DateUtil.formatTime(new Date()));
ThreadUtil.sleep(1000);
}
        Test.lock.unlock();
}
}

执行结果按线程start的顺序

Main thread is finished
李雷:15:33:54
李雷:15:33:55
李雷:15:33:56
韩梅梅:15:33:57
韩梅梅:15:33:58
韩梅梅:15:33:59
露西:15:34:00
露西:15:34:01
露西:15:34:02
莉莉:15:34:03
莉莉:15:34:04
莉莉:15:34:05