String字符串去重，保证顺序

    /**
     * 字符串去重
     *
     * @param str 待去重字符串  ABBACCDDEF
     * @return 去重后字符串     ABCDEF
     */
    public String removeDuplicate(String str) {
        if (str == null)
            return str;
        int len = str.length();
        if (len < 2)
            return str;
        char[] chars = str.toCharArray();
        int i, j;
        int index = 0;
        for (i = 0; i < len; ++i) {
            if (chars[i] != '\0') {
                chars[index++] = chars[i];
                for (j = i + 1; j < len; ++j) {
                    if (chars[j] == chars[i])
                        chars[j] = '\0';
                }
            }
        }
        return new String(chars);
    }




    /**
     * 删除相同字符连续出现
     *
     * @param s hello
     * @return helo
     */
    public static String uniqNearString(String s) {
        if (s == null)
            return "";
        StringBuilder sb = new StringBuilder();
        int i = 0, len = s.length();
        while (i < len) {
            char c = s.charAt(i);
            sb.append(c);
            i++;
            while (i < len && s.charAt(i) == c) {
                i++;
            }
        }
        return sb.toString();
    }