void JvmtiThreadState::add_env(JvmtiEnvBase *env) {

  {- -------------------------------------------
  (1) (assert)
      ---------------------------------------- -}

      assert(JvmtiThreadState_lock->is_locked(), "sanity check");

  {- -------------------------------------------
  (1) env 引数の JvmtiEnvBase オブジェクトに対応する
      新しい JvmtiEnvThreadState オブジェクトを生成する.
      ---------------------------------------- -}

      JvmtiEnvThreadState *new_ets = new JvmtiEnvThreadState(_thread, env);

  {- -------------------------------------------
  (1) 生成した JvmtiEnvThreadState オブジェクトを
      この JvmtiThreadState オブジェクト内に登録する.
      ---------------------------------------- -}

      // add this environment thread state to the end of the list (order is important)
      {
        // list deallocation (which occurs at a safepoint) cannot occur simultaneously
        debug_only(No_Safepoint_Verifier nosafepoint;)

        JvmtiEnvThreadStateIterator it(this);
        JvmtiEnvThreadState* previous_ets = NULL;
        for (JvmtiEnvThreadState* ets = it.first(); ets != NULL; ets = it.next(ets)) {
          previous_ets = ets;
        }
        if (previous_ets == NULL) {
          set_head_env_thread_state(new_ets);
        } else {
          previous_ets->set_next(new_ets);
        }
      }
    }