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(); } } |