java中ReentrantLock的作用是什么(java,reentrantlock,编程语言)

ReentrantLock称为重入锁，比内部锁synchonized拥有更强大的功能，它可中断、可定时、设置公平锁

【注】使用ReentrantLock时，一定要释放锁，一般释放放到finnal里写。

提供以下重要的方法

lock():获得锁，如果锁已被占用，则等待

lockInterruptibly():获得锁，但有限响应中断

unlock():释放锁

tryLock():尝试获取锁。如果获得，返回true；否则返回false

tryLock(long time, TimeUnit unit):在给定时间内获得锁。如果获得返回true；否则返回false

示例

例子1

一次执行结果：

Locked:firstThread
interupt begin
interupt end
UnLocked:firstThread
break before
Locked:secondThread
UnLocked:secondThread
Thread[secondThread,5,main] is Interupted
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at com.jihite.templet.JavaBase.ReentrantLockTest$1.run(ReentrantLockTest.java:23)
at java.lang.Thread.run(Thread.java:748)
Locked:secondThread
UnLocked:secondThread
break before

分析：firstThread执行，secondThread不停的判断是否可以获得锁，当firstThread执行完，secondThread执行后被打断

例子2

一次执行结果

Locked:firstThread
interupt begin
interupt end
Thread[secondThread,5,main] is Interupted
java.lang.InterruptedException
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireNanos(AbstractQueuedSynchronizer.java:936)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.tryAcquireNanos(AbstractQueuedSynchronizer.java:1247)
at java.util.concurrent.locks.ReentrantLock.tryLock(ReentrantLock.java:442)
at com.jihite.templet.JavaBase.ReentrantLockTest$1.run(ReentrantLockTest.java:19)
at java.lang.Thread.run(Thread.java:748)
Locked:secondThread
UnLocked:firstThread
break before
UnLocked:secondThread
break before

分析：firstThread执行，secondThread等待，等待过程被打断。打断后firstThread执行结束了，secondThread得到锁，继续执行

例子3

一次执行结果

Locked:firstThread
interupt begin
interupt end
UnLocked:firstThread
Locked:secondThread
UnLocked:secondThread
java.lang.InterruptedException: sleep interrupted
at java.lang.Thread.sleep(Native Method)
at com.jihite.templet.JavaBase.ReentrantLockTest2$1.run(ReentrantLockTest2.java:22)
at java.lang.Thread.run(Thread.java:748)
Locked:secondThread
UnLocked:secondThread

分析：firstThread先获得锁执行，secondThread在等待，此时中断并未打断等待。firstThread执行完，secondThread获取后被打断

例子4

一次执行结果

Locked:firstThread
interupt begin
interupt end
Exception in thread "secondThread" java.lang.IllegalMonitorStateException
at java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:151)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1261)
at java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:457)
at com.jihite.templet.JavaBase.ReentrantLockTest2$1.run(ReentrantLockTest2.java:25)
at java.lang.Thread.run(Thread.java:748)