code: private boolean removeMapping(Object key, Object value) {
          Object k = maskNull(key);
          Object[] tab = table;
          int len = tab.length;
          int i = hash(k, len);
  
          while (true) {
              Object item = tab[i];
              if (item == k) {
                  if (tab[i + 1] != value)
                      return false;
                  modCount++;
                  size--;
                  tab[i] = null;
                  tab[i + 1] = null;
                  closeDeletion(i);
                  return true;
              }
              if (item == null)
                  return false;
              i = nextKeyIndex(i, len);
          }
      }
docs: Removes the specified key-value mapping from the map if it is present.
  
  @param   key   possible key
  @param   value possible value
  @return  <code>true</code> if and only if the specified key-value
  mapping was in the map