MyTimeUtil--个人最常用时间管理方法

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

/**
 * @Author chenrd
 * @Date 2021-6-7 上午11:02:03
 * @Version 1.0 业务说明：本类默认时间格式采用yyyy-MM-dd
 *   
 */
public class MyTimeUtil {
    public static String fmtTime="yyyy-MM-dd";
    public static String fmtTimeStamp="yyyy-MM-dd HH:mm:ss";
    public static SimpleDateFormat sdf = new SimpleDateFormat(fmtTime);
    public static SimpleDateFormat sdfTime = new SimpleDateFormat(fmtTimeStamp);
    public static void main(String[] args) {

    }

    /**
     * 字符串的日期加上一天，在返回字符串
     */
    public static String addOneDay(String countdate) throws Exception {
        Calendar c = Calendar.getInstance();
        c.setTime(sdf.parse(countdate));
        c.add(Calendar.DATE, 1);
        String rtn = sdf.format(c.getTime());
        return rtn;
    }

    /**
     * 字符串的日期加上一天，在返回字符串
     */
    public static String subOneDay(String countdate) throws Exception {
        
        Calendar c = Calendar.getInstance();
        c.setTime(sdf.parse(countdate));
        c.add(Calendar.DATE, -1);
        String rtn = sdf.format(c.getTime());
        return rtn;
    }
    
    /**
     * @param countdate
     * @param num （负数就是减，正数就是加）
     * @return 字符串的日期加上自定义天，在返回字符串
     * @throws Exception 
     * String
     * 
     */
    public static String addSomeDay(String countdate,int num) throws Exception {
        Calendar c = Calendar.getInstance();
        c.setTime(sdf.parse(countdate));
        c.add(Calendar.DATE, num);
        String rtn = sdf.format(c.getTime());
        return rtn;
    }

    /**
     * @param countdate
     * @return 返回年第一天，如2021-01-01
     * @throws Exception 
     * String
     * 
     */
    public static String getYearfirstDay(String countdate) throws Exception {
        String rtn =  countdate.substring(0, countdate.length() - 5) + "01-01";
        return rtn;
    }
    /**
     * @param countdate
     * @return 返回年最后一天，如2021-12-12
     * @throws Exception 
     * String
     * 
     */
    public static String getYearLastDay(String countdate) throws Exception {
        String rtn =  countdate.substring(0, countdate.length() - 5) + "12-12";
        return rtn;
    }
    
    /**
     * 获取当月第一天(传参)
     * 
     * @return
     * @throws ParseException
     */
    public static Date getMonthFirstDay(String rq) throws ParseException {
        Calendar ca = Calendar.getInstance();
        ca.setTime(new SimpleDateFormat(fmtTime).parse(rq));
        ca.set(Calendar.DAY_OF_MONTH, ca.getActualMinimum(Calendar.DAY_OF_MONTH));
        return ca.getTime();
    }

    /**
     * 获取当月最后一天(传参)
     * 
     * @return
     * @throws ParseException
     */
    public static Date getMonthLastDay(String rq) throws ParseException {
        Calendar ca = Calendar.getInstance();
        ca.setTime(new SimpleDateFormat(fmtTime).parse(rq));
        ca.set(Calendar.DAY_OF_MONTH, ca.getActualMaximum(Calendar.DAY_OF_MONTH));
        return ca.getTime();
    }

    
    /**
     * 获取当前星期几
     *    调用方法， week(c.get(Calendar.DAY_OF_WEEK)) 
     * @return
     */
    public String week(int i) {
        String[] week = new String[] { "星期日","星期一", "星期二", "星期三", "星期四", "星期五", "星期六" };
        return week[i-1];
    }
}

 

 

遍历，月每天代码

 SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
  Calendar curCalendar = Calendar.getInstance();
 //去掉时分秒
  curCalendar.setTime(sdf.parse(sdf.format(curCalendar.getTime())));
 
 Calendar c = Calendar.getInstance();
 int allDay= c.getActualMaximum(Calendar.DAY_OF_MONTH);
 for (int i = 0; i < allDay; i++) {
            if (i != 0) {
                c.add(Calendar.DATE, 1);
            }
            
            时间不能超过今天，即只能查询到最新的是昨天的数据
            if (c.getTimeInMillis()-curCalendar.getTimeInMillis()<0) {
            
            }
 }

 

遍历，年每天代码

  SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
  Calendar curCalendar = Calendar.getInstance();
 //去掉时分秒
  curCalendar.setTime(sdf.parse(sdf.format(curCalendar.getTime())));
 
 Calendar c = Calendar.getInstance();
 int allDay= c.getActualMaximum(Calendar.DAY_OF_YEAR);365 0r 366
 for (int i = 0; i < allDay; i++) {
            if (i != 0) {
                c.add(Calendar.DATE, 1);
            }
            
            时间不能超过今天，即只能查询到最新的是昨天的数据
            if (c.getTimeInMillis()-curCalendar.getTimeInMillis()<0) {
            
            }
 }