void initialize_flags() {

  {- -------------------------------------------
  (1) TwoGenerationCollectorPolicy::initialize_flags() を呼んで, 
      ヒープサイズに関する各種コマンドラインオプション(特に 2世代の世代別 GC に関するもの)の値を調整する.
      ---------------------------------------- -}

        // Do basic sizing work
        this->TwoGenerationCollectorPolicy::initialize_flags();

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

        // If the user hasn't explicitly set the number of worker
        // threads, set the count.
        assert(UseSerialGC ||
               !FLAG_IS_DEFAULT(ParallelGCThreads) ||
               (ParallelGCThreads > 0),
               "ParallelGCThreads should be set before flag initialization");

  {- -------------------------------------------
  (1) MinSurvivorRatio と InitialSurvivorRatio を調整する.
      (どちらも, 値が 3 未満であれば 3 に切り上げる)
      ---------------------------------------- -}

        // The survivor ratio's are calculated "raw", unlike the
        // default gc, which adds 2 to the ratio value. We need to
        // make sure the values are valid before using them.
        if (MinSurvivorRatio < 3) {
          MinSurvivorRatio = 3;
        }

        if (InitialSurvivorRatio < 3) {
          InitialSurvivorRatio = 3;
        }
      }