jobject JNIHandles::make_local(JNIEnv* env, oop obj) {

  {- -------------------------------------------
  (1) もし引数の oop が NULL でなければ, 
      JNIHandleBlock::allocate_handle() で Thread::_active_handles 内に格納する.
      (引数が NULL の場合は何もしない)
      ---------------------------------------- -}

      if (obj == NULL) {
        return NULL;                // ignore null handles
      } else {
        JavaThread* thread = JavaThread::thread_from_jni_environment(env);
        assert(Universe::heap()->is_in_reserved(obj), "sanity check");
        return thread->active_handles()->allocate_handle(obj);
      }
    }