我想用 ReentrantLock
替换 syncronized
块以支持等待锁定的中断 . 为此,我使用 lockInterruptibly()
方法和惯用的try / finally块:
private ReentrantLock lock = new ReentrantLock();
try
{
lock.lockInterruptably();
}
catch( InterruptedException e )
{
Thread.currentThread.interrupt();
}
finally
{
lock.unlock();
}
问题是当InterruptedException发生时,也会发生最终的问题 . 这导致 IllegalMonitorStateException
,因为当前线程不保持锁定 .
这个简单的程序证明了这一点:
public class LockTest
{
public static void main( String[] args )
{
System.out.println("START");
Thread interruptThread = new Thread( new MyRunnable( Thread.currentThread() ) );
interruptThread.start();
ReentrantLock lock = new ReentrantLock();
Thread takeLockThread = new Thread( new TakeLockRunnable( lock ) );
takeLockThread.start();
try
{
Thread.sleep( 500 );
System.out.println("Trying to take lock on thread " + Thread.currentThread().getName());
lock.lockInterruptibly();
}
catch (InterruptedException e)
{
e.printStackTrace();
}
finally {
lock.unlock();
}
System.out.println( "DONE");
}
private static class MyRunnable implements Runnable
{
private Thread m_thread;
private MyRunnable( Thread thread)
{
m_thread = thread;
}
@Override
public void run()
{
try
{
Thread.sleep( 1000 );
}
catch (InterruptedException e)
{
// ignore
}
System.out.println( "Interrupting thread " + m_thread.getName() );
m_thread.interrupt();
}
}
private static class TakeLockRunnable implements Runnable
{
private ReentrantLock m_lock;
public TakeLockRunnable( ReentrantLock lock )
{
m_lock = lock;
}
@Override
public void run()
{
try
{
System.out.println("Taking lock on thread " + Thread.currentThread().getName());
m_lock.lock();
Thread.sleep( 20000 );
}
catch (Exception e)
{
e.printStackTrace();
}
finally {
m_lock.unlock();
}
}
}
}
它打印此输出:
START
Taking lock on thread Thread-1
Trying to take lock on thread main
java.lang.InterruptedException
at java.util.concurrent.locks.AbstractQueuedSynchronizer.doAcquireInterruptibly(AbstractQueuedSynchronizer.java:877)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireInterruptibly(AbstractQueuedSynchronizer.java:1201)
at java.util.concurrent.locks.ReentrantLock.lockInterruptibly(ReentrantLock.java:312)
at LockTest.main(LockTest.java:25)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
Exception in thread "main" java.lang.IllegalMonitorStateException
at java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:127)
at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1239)
at java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:431)
at LockTest.main(LockTest.java:32)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:120)
Interrupting thread main
有什么最好的方法来避免这种想法吗?
2 回答
lockInterruptibly()
调用应该在finally块之外 . 请注意,这总是尝试使用Lock
API(无论您使用lock()
还是lockInterruptibly()
),因为除非您已获得锁定,否则不希望执行"unlock"工作 .只需使用boolean-flag就可以解决这个问题: