How to verify whether the time format is correct in Java

In many scenarios, we need to verify whether the time and date are in the correct format, and whether the time conforms to the convention.

1. Verify the date in yyyy-MM-dd HH:mm:dd format

String date = "2020-01-25 12:36:45";
System.out.println("date "+isLegalDate(date.length(),date,"yyyy-MM-dd HH:mm:ss"));

2. Verify the date in yyyy-MM-dd format

String yearMonthday = "2020-01-01";
System.out.println("yearMonthday: "+isLegalDate(yearMonthday.length(),yearMonthday,"yyyy-MM-dd"));

3. Verify the date in yyyy-MM format

String yearMonth = "2020-02";
System.out.println("yearMonth: "+isLegalDate(yearMonth.length(),yearMonth,"yyyy-MM"));

4. Verify the date in yyyy format

String year = "2020";
System.out.println("year: "+isLegalDate(year.length(),year,"yyyy"));

5. Verify the date in HH:mm:ss format

String hms = "12:36:89";
System.out.println("hms: "+isLegalDate(hms.length(),hms,"HH:mm:ss"));

6. The following is a complete method class that can be run directly to verify whether the date format is correct

package com.shucha.deveiface.biz.test;

import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;

/**
 * @author tqf
 * @Description  时间格式校验
 * @Version 1.0
 * @since 2020-09-15 16:49
 */
public class IsLegalDate {


    public static void main(String[] args) {
        //1、验证 yyyy-MM-dd HH:mm:dd 格式的日期
        String date = "2020-01-25 12:36:45";
        System.out.println("date "+isLegalDate(date.length(),date,"yyyy-MM-dd HH:mm:ss"));

        //2、验证 yyyy-MM-dd 格式的日期
        String yearMonthday = "2020-01-01";
        System.out.println("yearMonthday: "+isLegalDate(yearMonthday.length(),yearMonthday,"yyyy-MM-dd"));

        //3、验证 yyyy-MM 格式的日期
        String yearMonth = "2020-02";
        System.out.println("yearMonth: "+isLegalDate(yearMonth.length(),yearMonth,"yyyy-MM"));

        //4、验证 yyyy 格式的日期
        String year = "2020";
        System.out.println("year: "+isLegalDate(year.length(),year,"yyyy"));

        //5、验证 HH:mm:ss 格式的日期
        String hms = "12:36:89";
        System.out.println("hms: "+isLegalDate(hms.length(),hms,"HH:mm:ss"));




    }

    /**
     * 根据时间 和时间格式 校验是否正确
     * @param length 校验的长度
     * @param sDate 校验的日期
     * @param format 校验的格式
     * @return
     */
    public static boolean isLegalDate(int length, String sDate,String format) {
        int legalLen = length;
        if ((sDate == null) || (sDate.length() != legalLen)) {
            return false;
        }
        DateFormat formatter = new SimpleDateFormat(format);
        try {
            Date date = formatter.parse(sDate);
            return sDate.equals(formatter.format(date));
        } catch (Exception e) {
            return false;
        }
    }
}

The following is a screenshot after time verification

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