JNIEXPORT void JNICALL
Java_sun_management_MemoryPoolImpl_setUsageThreshold0
  (JNIEnv *env, jobject pool, jlong current, jlong newThreshold)
{

  {- -------------------------------------------
  (1) jmm_SetPoolThreshold() を呼んで, usage threshold の 
      high threshold 及び low threshold を変更する.

      (なお, high threshold と low threshold の両方を指定された値に設定する.
       high が low を下回る瞬間があるとまずいので, 現在の閾値と指定された閾値の大小を見て, 
       どちらを先に変更するかを変えている.)
      ---------------------------------------- -}

        // Set both high and low threshold to the same threshold
        if (newThreshold > current) {
            // high threshold has to be set first so that high >= low
            jmm_interface->SetPoolThreshold(env, pool,
                                            JMM_USAGE_THRESHOLD_HIGH, newThreshold);
            jmm_interface->SetPoolThreshold(env, pool,
                                            JMM_USAGE_THRESHOLD_LOW, newThreshold);
        } else {
            // low threshold has to be set first so that high >= low
            jmm_interface->SetPoolThreshold(env, pool,
                                            JMM_USAGE_THRESHOLD_LOW, newThreshold);
            jmm_interface->SetPoolThreshold(env, pool,
                                            JMM_USAGE_THRESHOLD_HIGH, newThreshold);
        }
    }