方式一、同步方法

package com.string;import java.text.SimpleDateFormat;
import java.util.Date;//import com.jc.jdc.yellowcard.service.YellowCardService;
/*** 黄牌发行流水号，格式yyyyMMdd + '四位流水号' * @time 2019-09-10 19:02* @author wang-xiaoming**/
public class IssueNumberUtil_Syn {/*** 初始化发行号为null(0L)*/private static Long issueNumber = null;/*** 获取唯一发行号，这里可以把synchronized关键字去掉测试，会出现重复* @return* @throws Exception*/public static synchronized long getIssueNumber() throws Exception{if(issueNumber == null){/*// 服务器启动获取bean，当服务器需要重启或宕机时，重新获取bean，从数据库读取最大发行号YellowCardService yellowCardService = (YellowCardService) SpringBeanUtils.getBean("yellowCardService");// 获取数据库中的最大发行号// 为保险起见，yellowCardService.findMaxIssueNumber方法中也可以加把锁issueNumber = yellowCardService.findMaxIssueNumber();*/}issueNumber = (issueNumber == null || "".equals(issueNumber))? 201909090001L:issueNumber;SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMdd");long issueNumber1 = Long.parseLong(formatter.format(new Date()) + "0001");if(issueNumber1 > issueNumber){issueNumber = issueNumber1;return issueNumber;}else{return ++issueNumber;}}public static void main(String[] args) {// 多线程测试，模拟5000个线程同时调用getIssueNumber方法for (int i=0 ; i < 5000; i++) {new Thread(new Runnable() {@Overridepublic void run() {try {System.out.println(getIssueNumber());} catch (Exception e) {e.printStackTrace();}}}).start();}}}

方式二、同步对象锁

package com.string;import java.text.SimpleDateFormat;
import java.util.Date;//import com.jc.jdc.yellowcard.service.YellowCardService;
/*** 黄牌发行流水号，格式yyyyMMdd + '四位流水号'* @author wang-xiaoming**/
public class IssueNumberUtil_Lock {/*** 对象锁*/private static final Object lock = new Object();/*** 初始化发行号为null(0L)*/private static Long issueNumber = null;/*** 获取唯一发行号* @return* @throws Exception*/public static long getIssueNumber() throws Exception{synchronized (lock) {if(issueNumber == null){/*// 服务器启动获取bean，当服务器需要重启或宕机时，重新获取bean，从数据库读取最大发行号YellowCardService yellowCardService = (YellowCardService) SpringBeanUtils.getBean("yellowCardService");// 获取数据库中的最大发行号// 为保险起见，yellowCardService.findMaxIssueNumber方法中也可以加把锁issueNumber = yellowCardService.findMaxIssueNumber();*/}issueNumber = (issueNumber == null || "".equals(issueNumber))? 201909090001L:issueNumber;SimpleDateFormat formatter = new SimpleDateFormat("yyyyMMdd");long issueNumber1 = Long.parseLong(formatter.format(new Date()) + "0001");if(issueNumber1 > issueNumber){issueNumber = issueNumber1;return issueNumber;}else{return ++issueNumber;}}}public static void main(String[] args) {// 多线程测试，模拟5000个线程同时调用getIssueNumber方法for (int i=0 ; i < 5000; i++) {new Thread(new Runnable() {@Overridepublic void run() {try {System.out.println(getIssueNumber());} catch (Exception e) {e.printStackTrace();}}}).start();}}}

链接：https://pan.baidu.com/s/1ERRTTCcews4TlIM_2PzSFw
提取码：bakn