MemoryPool::MemoryPool(const char* name,
                       PoolType type,
                       size_t init_size,
                       size_t max_size,
                       bool support_usage_threshold,
                       bool support_gc_threshold) {

  {- -------------------------------------------
  (1) (フィールドの初期化)
      ---------------------------------------- -}

      _name = name;
      _initial_size = init_size;
      _max_size = max_size;
      _memory_pool_obj = NULL;
      _available_for_allocation = true;
      _num_managers = 0;
      _type = type;

      // initialize the max and init size of collection usage
      _after_gc_usage = MemoryUsage(_initial_size, 0, 0, _max_size);

      _usage_sensor = NULL;
      _gc_usage_sensor = NULL;
      // usage threshold supports both high and low threshold
      _usage_threshold = new ThresholdSupport(support_usage_threshold, support_usage_threshold);
      // gc usage threshold supports only high threshold
      _gc_usage_threshold = new ThresholdSupport(support_gc_threshold, support_gc_threshold);
    }