question: public static < V > int addDistinctList ( List < V > sourceList , List < V > entryList ) { if ( sourceList == null || isEmpty ( entryList ) ) { return 0 ; } int sourceCount = sourceList . size ( ) ; for ( V entry : entryList ) { if ( ! sourceList . contains ( entry ) ) { sourceList . add ( entry ) ; } } return sourceList . size ( ) - sourceCount ; }
target:  add all distinct entry to list1 from list2