Synchronized( this ) vs synchronized( SomeClass.class )

Question

I have seen synchronized bits of code declared in the following ways:
1)
synchronized( this )
  //some stuff
}2)
synchronized( SomeClass.class )
  //some stuff
}Could anyone explain the diference or tell me where to read about it.
Thanks In Adavance!

Answer 1

Mattbunch is correct, but I will also check later.
If you want to lock on a class level you lock on a
static method.The term "locking on a class level" doesn't really mean anything.
In the original post, the only difference betweensynchronized this() {} and synchronized(SomeClass.class) {} is which object they use as a lock. That's the only difference. There's no difference in what gets protected or how.
Static methods are at the class scope, global, and
they are locked for the class, not just the
instance, understand?Again, that statement--the concept of being "locked for the class vs. for the instance"--doesn't really have any meaning. If you declare a static method synchronized, it obtains one particular object's lock (that of the Class object corresponding to that method's class), and if you declare an instance method syncrhonized, it obtains a different object's lock--that of the intstance whose method you're calling. That's the only difference--which lock you obtain. There's no inherent difference in the scope of the "protection".
Also remember that locking on the static methods does
not prevent another thread from entering a non static
public method.You don't "lock on" a method. But assuming you mean "declaring a static method synchronized," it doesn't stop another thread from entering any other unsynchronized method, static or not, public or not, and it doesn't stop a thread from entering any synchronized instance method. It only stops threads from entering blocks or methods syncrhronized on the Class object for that class.