Java-学习日记（日期的转换与处理）

Java日期

主要是对日期进行相关操作，使用到的函数是Calendar,SimpleDateFormat(非线程安全，尽量避免使用)

对日期操作：Calendar

日期转换：FastDateFormat

/*实现提取前一天的日期*/
public class Main {
    public static final String DATE_FORMAT_YYYY_MM_DD = "yyyy-MM-dd";
    public static String dateToString(Date date, String pattern) {
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);
        return sdf.format(date);
    }
    public static Date stringToDate(String date, String pattern) {
        SimpleDateFormat sdf = new SimpleDateFormat(pattern);
        try {
            return sdf.parse(date);
        } catch (ParseException e) {
            e.printStackTrace();
        }
        return null;
    }
    public static String dateSubOneDate(String date)  {
        Calendar calendar = Calendar.getInstance();
        calendar.setTime(stringToDate(date, DATE_FORMAT_YYYY_MM_DD));
        calendar.add(Calendar.DATE, -1);//当前时间减去一天，即一天前的时间
        return dateToString(calendar.getTime(), DATE_FORMAT_YYYY_MM_DD);
    }

    public static void main(String[] args) throws ParseException {
        System.out.println(dateSubOneDate(dateToString(new Date(), DATE_FORMAT_YYYY_MM_DD)));
    }
}

/*得到今天的起始和结束日期*/
public static Date getTodayStartTime(Date date) {
        Calendar todayStart = Calendar.getInstance();
        todayStart.setTime(date);
        todayStart.set(Calendar.HOUR_OF_DAY, 0);
        todayStart.set(Calendar.MINUTE, 0);
        todayStart.set(Calendar.SECOND, 0);
        todayStart.set(Calendar.MILLISECOND, 0);
        return todayStart.getTime();
    }

    public static Date getTodayEndTime(Date date) {
        Calendar todayEnd = Calendar.getInstance();
        todayEnd.setTime(date);
        todayEnd.set(Calendar.HOUR_OF_DAY, 23);
        todayEnd.set(Calendar.MINUTE, 59);
        todayEnd.set(Calendar.SECOND, 59);
        todayEnd.set(Calendar.MILLISECOND, 999);
        return todayEnd.getTime();
    }

import org.apache.commons.lang3.time.DateFormatUtils;
import org.apache.commons.lang3.time.FastDateFormat;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.util.StringUtils;

import java.text.ParseException;
import java.time.LocalDateTime;
import java.time.format.DateTimeFormatter;
import java.util.Calendar;
import java.util.Date;

public class DateUtils {
    private static final Logger log = LoggerFactory.getLogger(DateUtils.class);

    public static Date getTodayStartTime(Date date) {
        Calendar todayStart = Calendar.getInstance();
        todayStart.setTime(date);
        todayStart.set(Calendar.HOUR_OF_DAY, 0);
        todayStart.set(Calendar.MINUTE, 0);
        todayStart.set(Calendar.SECOND, 0);
        todayStart.set(Calendar.MILLISECOND, 0);
        return todayStart.getTime();
    }

    public static Date getTodayEndTime(Date date) {
        Calendar todayEnd = Calendar.getInstance();
        todayEnd.setTime(date);
        todayEnd.set(Calendar.HOUR_OF_DAY, 23);
        todayEnd.set(Calendar.MINUTE, 59);
        todayEnd.set(Calendar.SECOND, 59);
        todayEnd.set(Calendar.MILLISECOND, 999);
        return todayEnd.getTime();
    }

    public static Date addDay(Date date, int day) {
        Calendar today = Calendar.getInstance();
        today.setTime(date);
        today.add(Calendar.DAY_OF_MONTH, day);
        return today.getTime();
    }


    public static Date parseStrToDate(String dateStr) {
        Date date;
        try {
            date = org.apache.commons.lang3.time.DateUtils.parseDate(dateStr, "yyyyMMdd");
        } catch (ParseException e) {
            return null;
        }
        return date;
    }

//    public static String formatDateToStr(Date date) {
//        FastDateFormat fdf = FastDateFormat.getInstance("yyyy年MM月dd日 HH:mm:ss");
//        return fdf.format(date);
//    }

    public static String formatDateToStr1(Date date) {
        FastDateFormat fdf = FastDateFormat.getInstance("yyyyMMdd");
        return fdf.format(date);
    }

    public static String formatDateToStr2(Date date) {
        FastDateFormat fdf = FastDateFormat.getInstance("yyyy-MM-dd HH:mm:ss");
        return fdf.format(date);
    }

    public static String formatDateToStr3(Date date) {
        FastDateFormat fdf = FastDateFormat.getInstance("yyyy年MM月dd日");
        return fdf.format(date);
    }

    public static String formatDateToStr4(long time) {
        FastDateFormat fdf = FastDateFormat.getInstance("yyyy-MM-dd HH:mm:ss");
        return fdf.format(time);
    }

    private static String testDate(String remark) {
        if (!StringUtils.isEmpty(remark) && remark.contains("_bill_")) {
            String tr = remark.replace("|", "");
            return tr.substring(tr.indexOf("B") + 1, tr.indexOf("_"));
        }
        return "";
    }

    public static String convertDate(String dateString) {
        DateTimeFormatter dtf = DateTimeFormatter.ofPattern("yyyyMMddHHmmss");
        String dateTime = null;
        try {
            LocalDateTime ldt = LocalDateTime.parse(dateString, dtf);
            DateTimeFormatter fa = DateTimeFormatter.ofPattern("yyyy-MM-dd HH:mm:ss");
            dateTime = ldt.format(fa);
        } catch (Exception e) {
            return dateString;
        }
        return dateTime;
    }


    public static String getDateStr(String dateStr) {
        if (StringUtils.isEmpty(dateStr)) {
            Date currentDate = new Date();
            Date date = new Date(currentDate.getTime() - 24 * 60 * 60 * 1000L);
            dateStr = DateFormatUtils.format(date, "yyyyMMdd");
        }
        return dateStr;
    }

}

import org.junit.Test;

import java.util.Date;

import static org.junit.Assert.*;
/**
 * @author  v-huyuqiao
 * @desc    TODO  
 * @create  2020/8/10 16:13
 **/
public class DateUtilsTest {
    @Test
    public void allDateTest(){
        System.out.println(DateUtils.getTodayStartTime(new Date()));        //20200810
        System.out.println(DateUtils.getTodayEndTime(new Date()));          // Mon Aug 10 23:59:59 CST 2020
        System.out.println(DateUtils.addDay(new Date(), 1));           //Tue Aug 11 16:08:03 CST 2020
        System.out.println(DateUtils.formatDateToStr1(new Date()));         //20200810
        System.out.println(DateUtils.formatDateToStr2(new Date()));         //2020-08-10 16:08:03
        System.out.println(DateUtils.formatDateToStr3(new Date()));         //2020年08月10日
        System.out.println(DateUtils.formatDateToStr4(System.currentTimeMillis())); //时间戳变成时间:2020-08-10 16:08:03
        System.out.println(DateUtils.convertDate("2020-08-10 00:00:00"));   //2020-08-10 00:00:00
        System.out.println(DateUtils.getDateStr(null));                     //20200809

    }
}