Securing variables global to a thread, i.e. class variables if a Callable object, against being spoiled by other threads using the same instance of the Callable object

Use the Thread Local Storage in any of the following situations

• when you use class variables in your Callable Object that are not read-only and you use the same Callable instance in more than one thread running in parallel
• when you use static variables in your Callable Object that are not read-only and more than one instances of the Callable may run in parallel threads.