Object intrinsic monitor as java.util.concurrent.Lock

问题

I believe it could be very useful to be able to use an object's monitor as a Lock. That is :

synchronized(object) {
    ...
}

would be equivalent to :

lock.lock();
try {
    ...
} finally {
    lock.unlock();
}

As far as i understand it, it is not possible to achieve this using Lock interface since synchronization only happens in blocks. A solution i see would be to have java.lang.Object be enriched with an extra method

public Lock asLock/getIntrinsicMonitorObject(); // Name isn't perfect but i'm not asking for that

or something like :

LockSupport.getIntrinsicMonitorObject(Object of);

---

Questions :

• Is there some good reasons it isn't possible to do this for now (i consider the fact that some tryLock isn't currently possible with synchronization isn't one)

• Is there some solution to do it using existing JRE classes ?

• Would a JSR on this make sense ?

回答1:

The Unsafe class* has some support to directly manipulate monitors:

public native void monitorEnter(Object o);

public native void monitorExit(Object o);

public native boolean tryMonitorEnter(Object o);

_{*that's in Java 8 but I think it was already there in Java 7}

来源：https://stackoverflow.com/questions/22375370/object-intrinsic-monitor-as-java-util-concurrent-lock