code: public final boolean unregister(final Object socketOrChannel)
      {
          if (socketOrChannel == null) {
              return false;
          }
          CompositePollItem items = this.items.remove(socketOrChannel);
          boolean rc = items != null;
          if (rc) {
              all.remove(items);
          }
          return rc;
      }
docs: Unregister a Socket or SelectableChannel for polling on the specified events.
  
  @param socketOrChannel   the Socket or SelectableChannel to be unregistered
  @return true if unregistered, otherwise false
  TODO would it be useful to unregister only for specific events ?