code: public long remove(K key)
    {
      if (key == null) {
        long old = _nullValue;
        _nullValue = NULL;
        return old;
      }
  
      int hash = key.hashCode() & _mask;
  
      while (true) {
        Object mapKey = _keys[hash];
  
        if (mapKey == null)
          return NULL;
        else if (mapKey.equals(key)) {
          _flags[hash] |= DELETED;
  
          _size--;
  
          _keys[hash] = null;
  
          return _values[hash];
        }
  
        hash = (hash + 1) & _mask;
      }
    }
docs: Deletes the entry.  Returns true if successful.