Static variables and multithreading in java

Question

Is a static member of a class present as only a single instance per process or thread? Meaning does each thread has its own copy of the static member variable of the class?

Answer 1

There is one copy of static variable per class-loader that loaded this class. This more-or-less means per-process, however you need to be aware of the difference.

E.g. when two web-apps have the same class bundled, the class will be loaded twice, thus having two copies of the same static field.

If you need a variable having independent value on a thread basis, have a look at ThreadLocal.