First, a bit of business: you may not have read our naming policy on the way in. It requires that you use a full, real (sounding) first and last name for your display name. Joke names, obviously fake names, and "handles" aren't OK here. You can change your display name here. Thanks!
As to your question: no, not intrinsically. All member variables -- both class and instance variables -- need to be properly protected from concurrent access.
They're only as safe as you make them, and there are many ways to make them unsafe. For example there's nothing safe about passing one instance variable to two other threads. There's nothing safe about two threads calling a method on your object which happens to reference an instance variable. You have to synchronize the method or use another lock to make them safe. Does that ring true?
A good question is never answered. It is not a bolt to be tightened into place but a seed to be planted and to bear more seed toward the hope of greening the landscape of the idea. John Ciardi