Topic: Java has no function level lock?

Java has no function level lock?

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Posted By: George_Simple
Posted On: Wednesday, March 19, 2003 03:53 AM

Hi, everyone! I am a C++ programmer before and after reading the internal implemention method of Java Thread. I think Java has no function level lock and only object level lock. I mean to acquire a function lock is the same as acquire an object's lock. For example, when objectA.synchronizedFunctionA is called, suppose synchronizedFunctionA is a synchronized function of class A. Java only check whether objectA is locked. The synchronized function synchronizedFunctionA has no individual function level lock. Am I correct? If I am correct, I think in some certain application, function level lock will be more efficient than object level lock. Even though it shou More>>

			

			Hi, everyone!
			

			

			

			I am a C++ programmer before and after reading the
			

			internal implemention method of Java Thread. I think
			

			Java has no function level lock and only object level
			

			lock. I mean to acquire a function lock is the same as
			

			acquire an object's lock.
			

			

			For example, when objectA.synchronizedFunctionA is called,
			

			suppose synchronizedFunctionA is a synchronized function of
			

			class A. Java only check whether objectA is locked. The synchronized function synchronizedFunctionA has no individual function level lock.
			

			

			Am I correct?
			

			

			If I am correct, I think in some certain application, function level lock will be more efficient than object level lock. Even though it should be used more carefully.
			

			

			Thanks in advance,
			

			George

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Re: Java has no function level lock?

Posted By: Marian_Olteanu
Posted On: Saturday, March 29, 2003 01:53 AM

If I understood right, you want to have synchronizedFunctionA non-static and you want that only one thread runs code in this function once.
Do this:


public class A
{
   private static final Object syncObjectA = new Object();
   public void synchronizedFunctionA( .... )
   {
      synchronized( syncObjectA )
      {
        // Your sync code
      }
   }
// Other stuff.......
}

So, you don't have to use singleton pattern or something like that. It is enough to allocate a static object for that method and use it for synchronization.

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Re: Java has no function level lock?

Posted By: Anonymous
Posted On: Wednesday, March 19, 2003 10:44 PM

There is one more way I can think of. Make the member function a synchronized static member function.

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Re: Java has no function level lock?

Posted By: Anonymous
Posted On: Wednesday, March 19, 2003 10:39 PM

You can make a class singleton and make the required methods
as synchronized methods. This will give you the so called
'function level lock'. I hope this helps you.

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