Java's threadlocal

The ThreadLocal data is stored in one thread and does not require lock synchronization. Theoretically ThreadLocal can be

So that a variable has a copy on each thread. ThreadLocal is commonly used to mask private variables of a thread, such as "and

or other resources. Also, it is used to maintain counters, statistics, or ID generation for each thread

Manager

See the Get method definitions commonly used by threadlocal:

  Public T get () {

        Thread T = Thread.CurrentThread ();

        Threadlocalmap map = getmap (t);

        if (map! = null) {

            Threadlocalmap.entry E = Map.getentry (this);

            if (E! = null) {

              &N Bsp @SuppressWarnings ("unchecked")

                T result = (t) e.value;

                return result;

           }

       }

        return setinitialvalue ();

   }

Threadlocalmap Getmap (Thread t) {

return t.threadlocals;

}

You can know that each thread has a threadlocal.threadlocalmap threadlocals inside, and the maintenance of this map is performed by Threadlocal. And it's initialized to be lazily.

The generation of the current nexthashcode for each threadlocal , and the generation of its index within the THREADLOCALMAP internal array, can be seen in the source code.

Java's threadlocal