公平锁

公平锁

示例：

public class Test4 {

   public static void main(String[] args) {
       TestReentrantlock test = new TestReentrantlock();// ReentrantLock有公平性
       // TestSync test = new TestSync(); synchronized没有公平性
       Thread t1 = new Thread(test);
       Thread t2 = new Thread(test);
       t1.start();
       t2.start();
   }
}

class TestReentrantlock extends Thread {
   // 向构造方法中传入true，定义一个公平锁
   private static ReentrantLock lock = new ReentrantLock(true);

   public void run() {
       for (int i = 0; i < 5; i++) {
           lock.lock();
           try {
               System.out.println(Thread.currentThread().getName() + " get lock");
           } finally {
               lock.unlock();
           }
       }
   }

}

class TestSync extends Thread {
   public void run() {
       for (int i = 0; i < 5; i++) {
           synchronized (this) {
               System.out.println(Thread.currentThread().getName() + " get lock in TestSync");
           }
       }
   }
}