Java 实现对敏感字符进行加密转换

 public static String cleanString(String aString) {
        if (aString == null) return null;
        String cleanString = "";
        for (int i = 0; i < aString.length(); ++i) {
            // charAt 方法返回字符串中某个字符在给定或指定索引处的 char 值
            cleanString += cleanChar(aString.charAt(i));
        }
        return cleanString;
    }

    private static char cleanChar(char aChar) {

        // 0 - 9
        for (int i = 48; i < 58; ++i) {
            if (aChar == i) return (char) i;
        }

        // 'A' - 'Z'
        for (int i = 65; i < 91; ++i) {
            if (aChar == i) return (char) i;
        }

        // 'a' - 'z'
        for (int i = 97; i < 123; ++i) {
            if (aChar == i) return (char) i;
        }

        // other valid characters
        switch (aChar) {
            case '/':
                return '/';
            case '.':
                return '.';
            case '-':
                return '-';
            case '_':
                return '_';
            case ' ':
                return ' ';
        }
        return '%';
    }