in short instance variables are shared among all threads accessing the same object. In contrast local variables are stored within a stack frame which is created for each method call. For this every thread calling a method gets its own copy of a local variable and can't interfere with other threads this way. Of course multi-threading is a lot more complicated but this is the basic difference between instance variables and local variables.
Marco
Post by:autobot
Alas, poor Yorick, he knew this tiny ad:
a bit of art, as a gift, the permaculture playing cards