Java simple time tool class

Tips before viewing:

The IDEA version used in this article is ultimate 2019.1, and the JDK version is 1.8.0_141.

This is a simple time tool class written by myself, including

1. Get the last n time of the current time (year/month/day...)

2. Convert to UTC time

3. Get the last day of the current month

4. Get the number of days in the current month

5. Get the number of days in the current year

6. Format time

Not much to say, just go to the code.

package testDate;

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

public class DateUtil {
    
    

    private static String YYYY_MM_DD = "yyyy-MM-dd";
    private static String YYYY_MM_DD_HH_MM_SS = "yyyy-MM-dd HH:mm:ss";
    private static String YYYY_MM_DD_T_HH_MM_SS_SSS_Z = "yyyy-MM-dd'T'HH:mm:ss.SSS'Z'";

    public static void main(String[] args) {
    
    

        // 前一年
        Date d1 = getLastNTime(Calendar.YEAR, -1);
        System.out.println("前一年：" + DateToStr(d1, YYYY_MM_DD_HH_MM_SS));
        // 后一天
        Date d2 = getLastNTime(Calendar.DATE, 1);
        System.out.println("后一天：" + DateToStr(d2, YYYY_MM_DD_HH_MM_SS));
        // 转化为UTC时间
        Date d3 = convertToUTC(new Date());
        System.out.println("UTC时间：" + DateToStr(d3, YYYY_MM_DD_T_HH_MM_SS_SSS_Z));
        // 获取当前月最后一天
        Date d4 = getCurrentMonthLastDay();
        System.out.println("当前月最后一天：" + DateToStr(d4, YYYY_MM_DD));
        // 获取当前月天数
        System.out.println("当前月天数：" + getCurrentMonthDayCount());
        // 获取当前年天数
        System.out.println("当前年天数：" + getCurrentYearDayCount());
    }

    /**
     * 获取当前时间的后n时间(年/月/日...）
     * @param timeType 时间类型（年/月/日...）
     * @param n
     * @return
     */
    private static Date getLastNTime(int timeType, int n){
    
    
        Calendar c = Calendar.getInstance();
        c.add(timeType, n);
        return c.getTime();
    }

    /**
     * 转化为UTC时间
     * @param date
     * @return
     */
    private static Date convertToUTC(Date date){
    
    
        Calendar c = Calendar.getInstance();
        c.setTime(date);
        // 时间偏移量
        int zoneOffset = c.get(Calendar.ZONE_OFFSET);
        // 夏令时差
        int dstOffset = c.get(Calendar.DST_OFFSET);
        // 从时间里扣除这些差量，即可以取得UTC时间
        c.add(Calendar.MILLISECOND, -(zoneOffset + dstOffset));
        return c.getTime();
    }

    /**
     * 获取当前月最后一天
     * @return
     */
    private static Date getCurrentMonthLastDay(){
    
    
        Calendar c = Calendar.getInstance();
        c.set(Calendar.DAY_OF_MONTH, c.getActualMaximum(Calendar.DAY_OF_MONTH));
        return c.getTime();
    }

    /**
     * 获取当前月天数
     * @return
     */
    private static int getCurrentMonthDayCount(){
    
    
        Calendar c = Calendar.getInstance();
        return c.getActualMaximum(Calendar.DAY_OF_MONTH);
    }

    /**
     * 获取当前年天数
     * @return
     */
    private static int getCurrentYearDayCount(){
    
    
        Calendar c = Calendar.getInstance();
        return c.getActualMaximum(Calendar.DAY_OF_YEAR);
    }

    /**
     * 格式化时间
     * @param date
     * @param formatType
     * @return
     */
    private static String DateToStr(Date date, String formatType){
    
    
        SimpleDateFormat sdf = new SimpleDateFormat(formatType);
        return sdf.format(date);
    }
}

The running result is shown in the figure below