code: protected T build() {
          if (encoder != null) {
              assert decoder != null;
              return buildFromCodec(decoder, encoder);
          }
  
          Http2Connection connection = this.connection;
          if (connection == null) {
              connection = new DefaultHttp2Connection(isServer(), maxReservedStreams());
          }
  
          return buildFromConnection(connection);
      }
docs: Create a new {@link Http2ConnectionHandler}.