code: private final java.util.Set getSubSet(final Object key)
      {
          // Make sure the hashcode is positive.
          return subSets[(int) ((key.hashCode() & 0x7FFFFFFF) % subSets.length)];
      }
docs: /*
  Compute the subSet containing a key.
  
  @param Object the key to be found.
  
  @return java.util.Set which could contain the key.