code: public V remove(Object key) {
      EntryImpl<K, V> entry = _entries[keyHash(key) & _mask];
      while (entry != null) {
        if (key.equals(entry._key)) {
          V prevValue = entry._value;
          removeEntry(entry);
          return prevValue;
        }
        entry = entry._next;
      }
      return null;
    }
docs: Removes the mapping for this key from this {@link FastMap} if present.
  
  @param key the key whose mapping is to be removed from the map.
  @return previous value associated with specified key,
  or <code>null</code> if there was no mapping for key.
  A <code>null</code> return can also indicate that the map
  previously associated <code>null</code> with the specified key.
  @throws NullPointerException if the key is <code>null</code>.