common_helper/src/main/java/com/xiongyingqi/util/SerializeHelper.java
private static String nextIndex() {
        String rs = "";
        synchronized (SerializeHelper.class) {
            rs += ++index < 0 ? -index : index;
            int least = 3 - rs.length();
            for (int i = 0; i < least; i++) {
                rs = "0" + rs;
            }
            return rs;
        }
    }
private static String nextIndex() {
        String rs = "";
        synchronized (SerializeHelper.class) {
            rs += ++index < 0 ? -index : index;
            int least = 3 - rs.length();
            for (int i = 0; i < least; i++) {
                rs = "0" + rs;
            }
            return rs;
        }
    }
返回固定长度的

@return