Re: Mutable Objects and Thread Boundaries

Peter Duniho wrote:


Yes, for volatile, this works. Volatile fields have special semantics
which prevent re-ordering reads and writes by the compiler, so this is
guaranteed to work.

I said it didn't work for all of the cases Joshua listed, particularily
the synchronized one. Replace the volatile with a synchronized block
and it won't work anymore.

Just trying to let other folks know what works and what doesn't. I
think you knew this already, just that you didn't touch all the bases
when you mentioned it originally.

class Test
{
   private boolean set;
   private int data;

   void methodA()
   {
     data = 5;
     synchronized( this ) {
        set = true;
     }
   }

   void methodB()
   {
     synchronized( this ) {
       if (set)
       {
         System.out.print(data); // may print "0"
       }
     }
   }
}