使用Lock对象实现同步效果

Lock是一个接口，为了使用一个Lock对象，需要用到

 

Lock lock = new ReentrantLock();

 

与 synchronized (someObject) 类似的，lock()方法，表示当前线程占用lock对象，一旦占用，其他线程就不能占用了。
与 synchronized 不同的是，一旦synchronized 块结束，就会自动释放对someObject的占用。 lock却必须调用unlock方法进行手动释放，为了保证释放的执行，往往会把unlock() 放在finally中进行。

 

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package multiplethread;   import java.text.SimpleDateFormat; import java.util.Date; import java.util.concurrent.locks.Lock; import java.util.concurrent.locks.ReentrantLock;   public class TestThread {       public static String now() {         return new SimpleDateFormat("HH:mm:ss").format(new Date());     }       public static void log(String msg) {         System.out.printf("%s %s %s %n", now() , Thread.currentThread().getName() , msg);     }       public static void main(String[] args) {         Lock lock = new ReentrantLock();           Thread t1 = new Thread() {             public void run() {                 try {                     log("线程启动");                     log("试图占有对象：lock");                       lock.lock();                       log("占有对象：lock");                     log("进行5秒的业务操作");                     Thread.sleep(5000);                   } catch (InterruptedException e) {                     e.printStackTrace();                 } finally {                     log("释放对象：lock");                     lock.unlock();                 }                 log("线程结束");             }         };         t1.setName("t1");         t1.start();         try {             //先让t1飞2秒             Thread.sleep(2000);         } catch (InterruptedException e1) {             // TODO Auto-generated catch block             e1.printStackTrace();         }         Thread t2 = new Thread() {               public void run() {                 try {                     log("线程启动");                     log("试图占有对象：lock");                       lock.lock();                       log("占有对象：lock");                     log("进行5秒的业务操作");                     Thread.sleep(5000);                   } catch (InterruptedException e) {                     e.printStackTrace();                 } finally {                     log("释放对象：lock");                     lock.unlock();                 }                 log("线程结束");             }         };         t2.setName("t2");         t2.start();     }   }