生成以日期开头，加4位数字，每次加1的工具类.如：201712140001

package com.infohold.smallpay.map.util.codebuild; import org.apache.log4j.Logger; import java.io.File; import java.text.DecimalFormat; import java.text.SimpleDateFormat; import java.util.Date; import java.util.List; /** * Created by wlh on 2017/12/14. */ public class CodeUtil { private static int width=4; //位数 private final static SimpleDateFormat sdf = new SimpleDateFormat("yyyyMMdd"); private static DecimalFormat df = null; private static final Logger log=Logger.getLogger(CodeUtil.class); public static synchronized String getNumber() { String result = null; try { File file=new File("SNumber.dat"); char[] chs = new char[width]; for (int i = 0; i < width; i++) { chs[i] = '0'; } df = new DecimalFormat(new String(chs)); Date current = new Date(); String date = sdf.format(current); int num = 1; if (file.exists()) { List< String > list = FileUtil.readList(file); String[] data = list.get(0).split(","); if (date.equals(data[0])) { num = Integer.parseInt(data[1]); } } FileUtil.rewrite(file, date + "," + (num + 1)); result = sdf.format(current) + df.format(num); } catch (Exception e) { log.error("生成id有误"); e.printStackTrace(); } return result; } }