question: public static Class < ? > findCommonElementType ( Collection < ? > collection ) { if ( isEmpty ( collection ) ) { return null ; } Class < ? > candidate = null ; for ( Object val : collection ) { if ( val != null ) { if ( candidate == null ) { candidate = val . getClass ( ) ; } else if ( candidate != val . getClass ( ) ) { return null ; } } } return candidate ; }
target:  Find the common element type of the given Collection, if any.