code: private void grow() {
          if (keys == null || nkeys >= keys.length) {
              String[] nk = new String[nkeys + 4];
              String[] nv = new String[nkeys + 4];
              if (keys != null)
                  System.arraycopy(keys, 0, nk, 0, nkeys);
              if (values != null)
                  System.arraycopy(values, 0, nv, 0, nkeys);
              keys = nk;
              values = nv;
          }
      }
docs: grow the key/value arrays as needed