Java代码：将Long类型的日期时间数据转换为指定格式字符串

今天遇到了这样一个场景：从数据库中取出的数据，日期信息（年月日）是以8位Long类型数字存放的（如20161116），时间信息（时分秒）是以6位Long类型数字存放的（如184253）。现需要将其转换为字符串，格式使用“yyyy-MM-dd HH:mm:ss”。

我写的工具类代码如下：

import java.text.MessageFormat;

public class DateTimeHelper {

    /**
     * 将8位数字转换为字符串yyyy-MM-dd
     * @param date
     * @return
     */
    public static String getDateString(Long date) {

        int year = 0;
        int month = 1;
        int day = 1;
        
        if (date != null) {
            int date_tmp = date.intValue();
            int year_tmp = date_tmp / 10000;
            int month_tmp = date_tmp % 10000 / 100;
            int day_tmp = date_tmp % 100;
            year = getValue(year_tmp, year, 0, 9999);
            month = getValue(month_tmp, month, 1, 12);
            switch (month) {
                case 1:
                case 3:
                case 5:
                case 7:
                case 8:
                case 10:
                case 12: {
                    day = getValue(day_tmp, day, 1, 31);
                } break;
                case 4:
                case 6:
                case 9:
                case 11:{
                    day = getValue(day_tmp, day, 1, 30);
                } break;
                case 2: {
                    if(year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
                        day = getValue(day_tmp, day, 1, 29);
                    } else {
                        day = getValue(day_tmp, day, 1, 28);
                    }
                } break;
            }
        }
        
        String result = MessageFormat.format("{0}-{1}-{2}", 
            String.format("%04d", year),
            String.format("%02d", month),
            String.format("%02d", day));
        return result;
    }
    
    /**
     * 将6位数字转换为字符串HH-mm-ss
     * @param time
     * @return
     */
    public static String getTimeString(Long time) {

        int hour = 0;
        int minute = 0;
        int second = 0;
        
        if (time != null) {
            int time_tmp = time.intValue();
            int hour_tmp = time_tmp / 10000;
            int minute_tmp = time_tmp % 10000 / 100;
            int second_tmp = time_tmp % 100;
            hour = getValue(hour_tmp, hour, 0, 23);
            minute = getValue(minute_tmp, minute, 0, 59);
            second = getValue(second_tmp, second, 0, 59);
        }
        
        String result = MessageFormat.format("{0}:{1}:{2}", 
            String.format("%02d", hour),
            String.format("%02d", minute),
            String.format("%02d", second));
        return result;
    }
    
    /**
     * 将8位数字转换为字符串yyyy-MM-dd 将6位数字转换为字符串HH-mm-ss
     * @param date
     * @param time
     * @return
     */
    public static String getDateTimeString(Long date, Long time) {
        return getDateString(date) + " " + getTimeString(time);
    }

    /**
     * 传入value值，如value在[min,max]内则返回value，否则返回默认值def
     * @param value
     * @param def
     * @param min
     * @param max
     * @return
     */
    private static int getValue(int value, int def, int min, int max) {
        return (value >= min && value <= max) ? value : def;
    }
}

内含三个函数：

1、public static String getDateString(Long date)

给定8位数字，如20161116L，返回yyyy-MM-dd格式字符串，如2016-11-16

2、public static String getTimeString(Long time)

给定6位数字，如184253L，返回HH:mm:ss格式字符串，如18:42:53

3、public static String getDateTimeString(Long date, Long time)

功能1和功能2的合集，返回yyyy-MM-dd HH:mm:ss格式字符串，如2016-11-16 18:42:53

其中，日期（年月日）的格式为{0}-{1}-{2}，时间（时分秒）的格式为{0}:{1}:{2}，可根据实际情况自行改动

测试调用代码如下：

public class JavaTest {
    public static void main(String[] args) {

        System.out.println("---getDateString---");
        System.out.println(DateTimeHelper.getDateString(null));
        System.out.println(DateTimeHelper.getDateString(20161116L));
        System.out.println(DateTimeHelper.getDateString(99999999L));

        System.out.println("---getTimeString---");
        System.out.println(DateTimeHelper.getTimeString(null));
        System.out.println(DateTimeHelper.getTimeString(160511L));
        System.out.println(DateTimeHelper.getTimeString(999999L));

        System.out.println("---getDateTimeString---");
        System.out.println(DateTimeHelper.getDateTimeString(null, null));
        System.out.println(DateTimeHelper.getDateTimeString(20161116L, null));
        System.out.println(DateTimeHelper.getDateTimeString(null, 160511L));
        System.out.println(DateTimeHelper.getDateTimeString(20161116L, 160511L));
        System.out.println(DateTimeHelper.getDateTimeString(99999999L, 999999L));
    }
}

程序运行结果如下：

---getDateString---
0000-01-01
2016-11-16
9999-01-01
---getTimeString---
00:00:00
16:05:11
00:00:00
---getDateTimeString---
0000-01-01 00:00:00
2016-11-16 00:00:00
0000-01-01 16:05:11
2016-11-16 16:05:11
9999-01-01 00:00:00

END

来源：oschina

链接：https://my.oschina.net/u/1425762/blog/789302