question: public RepeatedFieldBuilder < MType , BType , IType > addMessage ( MType message ) { if ( message == null ) { throw new NullPointerException ( ) ; } ensureMutableMessageList ( ) ; messages . add ( message ) ; if ( builders != null ) { builders . add ( null ) ; } onChanged ( ) ; incrementModCounts ( ) ; return this ; }
target:  Appends the specified element to the end of this list.