@Override
 public int test() {
   final Int2ObjectOpenHashMap<Integer> m_map =
       new Int2ObjectOpenHashMap<>(m_keys.length, m_fillFactor);
   for (int i = 0; i < m_keys.length; ++i) m_map.put(m_keys[i], null);
   for (int i = 0; i < m_keys.length; ++i) m_map.put(m_keys[i], null);
   return m_map.size();
 }
 @Override
 public int test() {
   final Int2ObjectOpenHashMap<Integer> m_map =
       new Int2ObjectOpenHashMap<>(m_keys.length / 2 + 1, m_fillFactor);
   final Integer value = 1;
   int add = 0, remove = 0;
   while (add < m_keys.length) {
     m_map.put(m_keys[add], value);
     ++add;
     m_map.put(m_keys[add], value);
     ++add;
     m_map.remove(m_keys[remove++]);
   }
   return m_map.size();
 }