java 36进制加一进位,10位字符串，从0000000000开始

/**

 * 36进制加一进位,10位字符串，从0000000000开始
 *
 * @param old 旧的字符串
 * @return 进一后的字符串
 */
public static String stringIncrease(String old) {
    char[] ss = old.toCharArray();
    int length = 10;
    for (int i = length - 1; i >= 0; i--) {
        int temp = ss[i];
        int number9 = '9';
        int numberZ = 'z';
        if (temp < number9 - 1) {
            ss[i] = (char) ((int) ss[i] + 1);
            break;
        } else if (temp == number9) {
            ss[i] = 'a';
            break;
        } else if (temp < numberZ) {
            ss[i] = (char) ((int) ss[i] + 1);
            break;
        } else {
            ss[i] = '0';
        }
    }
    return new String(ss);
}