“If you are porting a single-threaded application to a multithreaded environment, you can preserve thread safety by converting shared global variables into ThreadLocals, if the semantics of the shared globals permits this; an applicationwide cache would not be as useful if it were turned into a number of thread-local caches. ThreadLocal is widely used in implementing application frameworks. For example, J2EE containers associate a transaction context with an executing thread for the duration of an EJB call. This is easily implemented using a static Thread-Local holding the transaction context: when”