question: public static String insert ( final String value , final String substr , final int index ) { validate ( value , NULL_STRING_PREDICATE , NULL_STRING_MSG_SUPPLIER ) ; validate ( substr , NULL_STRING_PREDICATE , NULL_STRING_MSG_SUPPLIER ) ; if ( index > value . length ( ) ) { return value ; } return append ( value . substring ( 0 , index ) , substr , value . substring ( index ) ) ; }
target:  Inserts 'substr' into the 'value' at the 'index' provided.