question: private static boolean isValidScheme ( final String scheme ) { final int length = scheme . length ( ) ; if ( length <= 0 ) { return false ; } char c = scheme . charAt ( 0 ) ; if ( ! Character . isLetter ( c ) ) { return false ; } for ( int i = 1 ; i < length ; i ++ ) { c = scheme . charAt ( i ) ; if ( ! Character . isLetterOrDigit ( c ) && c != '.' && c != '+' && c != '-' ) { return false ; } } return true ; }
target:  Checks if it is a valid scheme.