question: @ Override public void actionPerformed ( ActionEvent e ) { Object o ; o = e . getSource ( ) ; if ( o == menuItemMean ) { calcMean ( ) ; } else if ( o == menuItemSetAllValues ) { setValues ( menuItemSetAllValues ) ; } else if ( o == menuItemSetMissingValues ) { setValues ( menuItemSetMissingValues ) ; } else if ( o == menuItemReplaceValues ) { setValues ( menuItemReplaceValues ) ; } else if ( o == menuItemRenameAttribute ) { renameAttribute ( ) ; } else if ( o == menuItemAttributeAsClass ) { attributeAsClass ( ) ; } else if ( o == menuItemDeleteAttribute ) { deleteAttribute ( ) ; } else if ( o == menuItemDeleteAttributes ) { deleteAttributes ( ) ; } else if ( o == menuItemDeleteSelectedInstance ) { deleteInstance ( ) ; } else if ( o == menuItemDeleteAllSelectedInstances ) { deleteInstances ( ) ; } else if ( o == menuItemSortInstances ) { sortInstances ( ) ; } else if ( o == menuItemSearch ) { search ( ) ; } else if ( o == menuItemClearSearch ) { clearSearch ( ) ; } else if ( o == menuItemUndo ) { undo ( ) ; } else if ( o == menuItemCopy ) { copyContent ( ) ; } else if ( o == menuItemOptimalColWidth ) { setOptimalColWidth ( ) ; } else if ( o == menuItemOptimalColWidths ) { setOptimalColWidths ( ) ; } }
target:  invoked when an action occurs