/**
     * 删除字符串首尾指定字符
     */
    public static String customTrim(String str, char c) {
        char[] chars = str.toCharArray();
        int len = chars.length;
        int st = 0;
        while ( (st < len) && (chars[st] == c) ){
            st ++;
        }
        while ( (st < len) && (chars[len-1] == c) ){
            len --;
        }

        return (st > 0) || (len < chars.length) ? str.substring(st, len) : str;
    }
     //首
    public static String customLtrim(String str, char c) {
        char[] chars = str.toCharArray();
        int len = chars.length;
        int st = 0;
        while ( (st < len) && (chars[st] == c) ){
            st ++;
        }
        return (st > 0) ? str.substring(st, len) : str;
    }
   //尾
    public static String customRtrim(String str, char c) {
        char[] chars = str.toCharArray();
        int len = chars.length;
        int st = 0;
        while ( (st < len) && (chars[len-1] == c) ){
            len --;
        }
        return (len < chars.length) ? str.substring(st, len) : str;
    }