====== Java ThreadLocal ======
  * [[http://docs.oracle.com/javase/7/docs/api/java/lang/ThreadLocal.html|ThreadLocal]]

  Each thread holds an implicit reference to its copy of a thread-local variable
  as long as the thread is alive and the ThreadLocal instance is accessible;
  after a thread goes away, all of its copies of thread-local instances are subject 
  to garbage collection (unless other references to these copies exist).

===== 참조 =====
  * [[http://stackoverflow.com/questions/17968803/threadlocal-memory-leak|java - ThreadLocal & Memory Leak]]