question: protected void ensureRowsAreVisible ( int beginRow , int endRow ) { if ( tree != null && beginRow >= 0 && endRow < getRowCount ( tree ) ) { boolean scrollVert = DefaultLookup . getBoolean ( tree , this , "Tree.scrollsHorizontallyAndVertically" , false ) ; if ( beginRow == endRow ) { Rectangle scrollBounds = getPathBounds ( tree , getPathForRow ( tree , beginRow ) ) ; if ( scrollBounds != null ) { if ( ! scrollVert ) { scrollBounds . x = tree . getVisibleRect ( ) . x ; scrollBounds . width = 1 ; } tree . scrollRectToVisible ( scrollBounds ) ; } } else { Rectangle beginRect = getPathBounds ( tree , getPathForRow ( tree , beginRow ) ) ; if ( beginRect != null ) { Rectangle visRect = tree . getVisibleRect ( ) ; Rectangle testRect = beginRect ; int beginY = beginRect . y ; int maxY = beginY + visRect . height ; for ( int counter = beginRow + 1 ; counter <= endRow ; counter ++ ) { testRect = getPathBounds ( tree , getPathForRow ( tree , counter ) ) ; if ( testRect == null ) { return ; } if ( ( testRect . y + testRect . height ) > maxY ) counter = endRow ; } tree . scrollRectToVisible ( new Rectangle ( visRect . x , beginY , 1 , testRect . y + testRect . height - beginY ) ) ; } } } }
target:  Ensures that the rows identified by beginRow through endRow are visible.