question: private static Set < String > duplicateFields ( Class cls ) { Set < String > all = new HashSet < > ( ) ; Set < String > duplicates = new HashSet < > ( ) ; for ( Class < ? > c = cls ; c != null && ! c . equals ( Object . class ) ; c = c . getSuperclass ( ) ) { for ( Field f : c . getDeclaredFields ( ) ) { if ( serializeField ( f ) ) { String name = f . getName ( ) ; if ( ! all . add ( name ) ) duplicates . add ( name ) ; } } } return duplicates ; }
target:  Find all fields with duplicate names in the class.