获取锁定
- void lock()：常用获取锁定的方法
- void lockInterruptibly()：如果当前线程未被中断，则获取锁定；如果当前线程被中断，则出现异常
- boolean tryLock()：调用时锁定未被另一个线程持有的情况下，才会获取该锁定
- boolean tryLock(long timeOut,TimeUnit unit)：如果锁定在给定时间内未被另一个线程持有，且当前线程未被中断，则获取该锁定
lock()方法
1 public class Run { 2 private ReentrantLock lock = new ReentrantLock(); 3 4 public void testLock(){ 5 try { 6 lock.lock(); 7 8 for (int i = 0; i < 5; i++) { 9 System.out.println("ThreadName = "+Thread.currentThread().getName()+", i = "+(i+1)); 10 } 11 System.out.println(Thread.currentThread().getName()+"线程执行完毕，当前时间："+System.currentTimeMillis()); 12 Thread.sleep(1000); 13 } catch (InterruptedException e) { 14 e.printStackTrace(); 15 } finally { 16 lock.unlock(); 17 } 18 } 19 public static void main(String[] args) { 20 Run run = new Run(); 21 run.testLock(); 22 23 Runnable runnable = new Runnable() { 24 @Override 25 public void run() { 26 run.testLock(); 27 } 28 }; 29 Thread threadA = new Thread(runnable); 30 threadA.setName("A"); 31 threadA.start(); 32 Thread threadB = new Thread(runnable); 33 threadB.setName("B"); 34 threadB.start(); 35 } 36 }
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ThreadName = main, i = 1 ThreadName = main, i = 2 ThreadName = main, i = 3 ThreadName = main, i = 4 ThreadName = main, i = 5 main线程执行完毕，当前时间：1539138509575 ThreadName = A, i = 1 ThreadName = A, i = 2 ThreadName = A, i = 3 ThreadName = A, i = 4 ThreadName = A, i = 5 A线程执行完毕，当前时间：1539138510587 ThreadName = B, i = 1 ThreadName = B, i = 2 ThreadName = B, i = 3 ThreadName = B, i = 4 ThreadName = B, i = 5 B线程执行完毕，当前时间：1539138511587
lockInterruptibly()方法
1 public class Run2 { 2 private ReentrantLock lock = new ReentrantLock(); 3 public void testLockInterruptibly(){ 4 try { 5 lock.lockInterruptibly(); 6 System.out.println("ThreadName = "+Thread.currentThread().getName()); 7 } catch (InterruptedException e) { 8 e.printStackTrace(); 9 } finally { 10 if(lock.isHeldByCurrentThread()){//查询当前线程是否保持锁定 11 lock.unlock(); 12 } 13 } 14 } 15 16 public static void main(String[] args) { 17 Run2 run2 = new Run2(); 18 Runnable runnable = new Runnable() { 19 @Override 20 public void run() { 21 run2.testLockInterruptibly(); 22 } 23 }; 24 Thread t1 = new Thread(runnable); 25 t1.setName("T1"); 26 t1.start(); 27 28 Thread t2 = new Thread(runnable); 29 t2.setName("T2"); 30 t2.start(); 31 t2.interrupt(); 32 } 33 }
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java.lang.InterruptedException ThreadName = T1 at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1220) at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:335) at com.qf.test12.t.Run2.testLockInterruptibly(Run2.java:13) at com.qf.test12.t.Run2$1.run(Run2.java:29) at java.lang.Thread.run(Thread.java:748)
tryLock()方法
1 public class Run3 { 2 private ReentrantLock lock = new ReentrantLock(); 3 public void testTryLock(){//只获取锁定，不释放锁定 4 if(lock.tryLock()){ 5 System.out.println(Thread.currentThread().getName()+"获得锁"); 6 }else { 7 System.out.println(Thread.currentThread().getName()+"未获得锁"); 8 } 9 } 10 11 public static void main(String[] args) { 12 Run3 run3 = new Run3(); 13 Runnable runnable = new Runnable() { 14 @Override 15 public void run() { 16 run3.testTryLock(); 17 } 18 }; 19 Thread threadA = new Thread(runnable); 20 threadA.setName("A"); 21 threadA.start(); 22 Thread threadB = new Thread(runnable); 23 threadB.setName("B"); 24 threadB.start(); 25 } 26 }
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A获得锁
B未获得锁
tryLock(long timeOut,TimeUnit unit)方法
1 public class Run3 { 2 private ReentrantLock lock = new ReentrantLock(); 3 public void testTryLock(){ 4 try { 5 if(lock.tryLock(3, TimeUnit.SECONDS)){ 6 System.out.println(Thread.currentThread().getName()+"获得锁"); 7 Thread.sleep(4000);//有一个未获得锁 8 //Thread.sleep(2000);//两个都获得锁 9 }else { 10 System.out.println(Thread.currentThread().getName()+"未获得锁"); 11 } 12 } catch (InterruptedException e) { 13 e.printStackTrace(); 14 } finally { 15 if(lock.isHeldByCurrentThread()){ 16 lock.unlock(); 17 } 18 } 19 } 20 21 public static void main(String[] args) { 22 Run3 run3 = new Run3(); 23 Runnable runnable = new Runnable() { 24 @Override 25 public void run() { 26 System.out.println(Thread.currentThread().getName()+"执行，当前时间："+System.currentTimeMillis()); 27 run3.testTryLock(); 28 } 29 }; 30 Thread threadA = new Thread(runnable); 31 threadA.setName("A"); 32 threadA.start(); 33 Thread threadB = new Thread(runnable); 34 threadB.setName("B"); 35 threadB.start(); 36 } 37 }
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--------------------Thread.sleep(4000)------------------- A执行，当前时间：1539141085501 B执行，当前时间：1539141085501 B获得锁 A未获得锁 --------------------Thread.sleep(2000)------------------- A执行，当前时间：1539141269380 B执行，当前时间：1539141269380 A获得锁 B获得锁
其他常用方法
getXxx方法
- int getHoldCount()方法：查询当前线程保持此锁定的个数，即当前线程调用lock()方法的次数
- int getQueueLength()方法：返回正在等待此锁定的线程估计数
- int getWaitQueueLength(Condition condition)方法：返回等待与此锁定相关的给定条件的线程估计数
hasXxx方法
- hasQueuedThread()