How to generate numbers automatically by java

This article mainly introduces how to automatically generate the number of java, has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand it.

The details are as follows

/ * automatically generate numbering format: yyMM+ four-digit serial number * / @ RequestMapping (params = "createCode") @ ResponseBody public AjaxJson createCode (HttpServletRequest request, String tableName, String fieldName) {AjaxJson j = new AjaxJson (); String sql = "select Max (a." + fieldName + ") max_code from" + tableName + "a"; List list = new ArrayList (); list = jdbcTemplate.queryForList (sql) / / System.out.println ("maximum number:" + list.get (0). Get ("max_comment_code")); String comment_code = ""; String max_code = ""; if (list.size () > 0) {max_code = (String) list.get (0). Get ("max_code");} SimpleDateFormat format = new SimpleDateFormat ("yyMM"); / / time string generation method String uid_pfix = format.format (new Date ()) / / combine the first part of the serial number, the time string, such as: 1601 System.out.println ("time=" + format.format (new Date (); if (max_code! = null & & max_code.contains (uid_pfix)) {String uid_end= max_code.substring (4,8); / / intercept the last four digits of the string. Result: 0001 / / System.out.println ("uid_end=" + uid_end) Int endNum= Integer.parseInt (uid_end); / / convert 0001 of String type to 1 / / System.out.println of int type ("endNum=" + endNum); int tmpNum= 10000 + endNum + 1; / / result 10002 / / System.out.println ("tmpNum=" + tmpNum); comment_code = uid_pfix + UtilMethod.subStr ("" + tmpNum, 1) / remove the first 1 of 10002 and spell it into a 1601260002 string} else {comment_code = uid_pfix + "0001";} / / System.out.println (comment_code); Map map = new HashMap (); map.put ("msg", comment_code); j.setAttributes (map); return j } / / Public method public class UtilMethod {/ * * how to remove the first 1 of 10002: * @ param str * @ param start * @ return * / public static String subStr (String str, int start) {if (str = = null | | str.equals (") | | str.length () = = 0) return"; if (start < str.length ()) {return str.substring (start) } else {return ";}

Front end:

/ / automatically generate numbers; format: yyMM0001function createCode () {var id = $("[name='id']") .val (); / / alert (id.length); if (id.length)