ThreadLocal is the class you can use for that.

One main advantage I found (in fact my requirement) is that thread itself can carry information with it. Which means if you have a method

processFile(String fileName)

Using ThreadLocal you can pass additional information to this method apart from the String fileName parameter, which will be carried safely inside the thread executing it. Its useful especially when you have a big chain of method calls and you need to pass an additional information to the last method from the first one. Using ThreadLocal you just need to update the first method to set the additional information and last method to read from it.

Another obvious advantage is its thread safe!!! Its local to a thread, so no other thread can access it. For the same reason Spring stores the session variable as ThreadLocal.