Threads, synchronization, etc... (unable to make it works)

Hello,

I can't understand why this don't work (interestingly, sometimes
works, but not always).
Imagine this situation: (I'll speak about "parent" and "children" in a
different sense than object programming, ok?)
A "parent" java class that creates a new "child" class running in a
new thread, and then this java class starts a new thread for itself
and in the run method, starts a new "child" class. Both "children"
classes have a pointer to the "parent" creator, which have pointers to
both children. Let's call the children A and B.

The problem is I want children A to read a public atribute of children
B, but it doesn't work!!! (calling A.parent.B) (sometimes it does,
what makes the thing more extrange)

Could you iluminate me, please? (answers also to my email address if
posible, please)

Thanks in advance,
Federico