1.Spring 自带的

    /**
     * 计算cron表达式近n次时间-(6段-秒 分 时 日 月 周)
     *
     * @param cronExpression cron表达式
     * @param cronCount      下几次运行时间
     * @param maxCronCount   最大执行次数
     * @return List<String>
     */
    @RequestMapping(value = "listCronRunTime")
    public AjaxResult listCronRunTime(
            @RequestParam(value = "cronExpression", required = false) String cronExpression,
            @RequestParam(value = "cronCount", required = false, defaultValue = "1") Integer cronCount,
            @RequestParam(value = "maxCronCount", required = false, defaultValue = "100") Integer maxCronCount) {
        if (StringUtils.isBlank(cronExpression)) {
            return new AjaxResult(-1, "Cron 表达式不能为空!");
        }
        if (!CronSequenceGenerator.isValidExpression(cronExpression)) {
            return new AjaxResult(-1, "Cron格式不正确,Cron：" + cronExpression);
        }
        if (cronCount < 1) {
            cronCount = 1;
        }
        if (maxCronCount < 1) {
            maxCronCount = 100;
        }
        if (cronCount > maxCronCount) {
            cronCount = maxCronCount;
        }
        CronSequenceGenerator cronSequenceGenerator = new CronSequenceGenerator(cronExpression);
        List<String> cronTimeList = new ArrayList<>();
        Date nextTimePoint = new Date();
        SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        for (int i = 0; i < cronCount; i++) {
            nextTimePoint = cronSequenceGenerator.next(nextTimePoint);
            cronTimeList.add(sdf.format(nextTimePoint));
        }
        return new AjaxResult(cronTimeList);
    }

2.第二种 Quartz

首先引入maven依赖或者引入jar(本来就有定时任务的,此步骤省略)

<dependency>
    <groupId>org.quartz-scheduler</groupId>
    <artifactId>quartz</artifactId>
    <version>2.3.0</version>
</dependency>

(1).

/**
 *
 * @param cronExpression    cron表达式
 * @param numTimes    下几次运行时间
 * @return
 */
public static List<String> getNextExecTime(String cronExpression,Integer numTimes) {
        List<String> list = new ArrayList<>();
        CronTriggerImpl cronTriggerImpl = new CronTriggerImpl();
        try {
            cronTriggerImpl.setCronExpression(cronExpression);
        } catch(ParseException e) {
            e.printStackTrace();
        }
        // 这个是重点，一行代码搞定
        List<Date> dates = TriggerUtils.computeFireTimes(cronTriggerImpl, null, numTimes);
        SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");
        for (Date date : dates) {
            list.add(dateFormat.format(date));
        }
        return list;
}

(2).

    /**
     * 最近n次运行时间 Date[]-(7段-秒 分 时 日 月 周 年)
     *
     * @param cron  表达式
     * @param count 运行次数
     */
    public static Date[] getCronScheduledDate(String cron, Integer count) {
        if (!CronExpression.isValidExpression(cron)) {
            System.out.println("定时任务Cron格式不正确,Cron：" + cron);
            return null;
        }
        if (count == null || count < 1) {
            count = 1;
        }
        Date[] dateArray = new Date[count];
        CronTrigger trigger = TriggerBuilder.newTrigger().withIdentity("Caclulate Date").withSchedule(CronScheduleBuilder.cronSchedule(cron)).build();
        Date time0 = trigger.getStartTime();
        Date time1 = trigger.getFireTimeAfter(time0);
        dateArray[0] = time1;
        if (dateArray.length > 1) {
            Date timeTemp = time1;
            for (int i = 1; i < dateArray.length; i++) {
                timeTemp = trigger.getFireTimeAfter(timeTemp);
                if (timeTemp != null) {
                    dateArray[i] = timeTemp;
                } else {
                    break;
                }
            }
        }
        return dateArray;
    }

检验表达式是否正确(spring + quartz)

    /**
     * 检验表达式是否正确-spring(org.springframework.scheduling.support.CronSequenceGenerator)
     *
     * @param cron cron表达式
     * @return 正确:true
     */
    public static boolean cronValidExpressionFlag(String cron) {
        return StringUtils.isNotBlank(cron) && CronSequenceGenerator.isValidExpression(cron);
    }
    /**
     * 检验表达式是否正确-quartz(org.quartz.CronExpression)
     *
     * @param cron cron表达式
     * @return 正确:true
     */
    public static boolean cronValidExpressionFlag(String cron) {
        return StringUtils.isNotBlank(cron) && CronExpression.isValidExpression(cron);
    }