java 根据当前日期，获取当周，月开始和结束日期

冷不防 2024-02-21 11:49 48阅读 0赞

#### 根据当前时间获取当月开始和结束日期 ####

*  1、根据当前时间获取当月开始和结束日期
 *  2、根据当前日期获取一周的开始和结束日期

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## 1、根据当前时间获取当月开始和结束日期 ##

import java.util.Calendar;
    import java.util.Date;
    
    /**
     * @Author Mouoal
     * @Description: 说明用途
     * @Date 2023/10/19 9:41
     * @Version 1.0
     */
    public class DateUtils {
        
        public static Date getCurrentDate() {
        
            String ds = "202030913";
            return new Date();
        }
    
    
    
        public static Date getFirstDayOfMonth(Date date) {
        
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(date);
            calendar.set(Calendar.DAY_OF_MONTH, 1);
            return calendar.getTime();
        }
    
        public static Date getLastDayOfMonth(Date date) {
        
            Calendar calendar = Calendar.getInstance();
            calendar.setTime(date);
            calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));
            return calendar.getTime();
        }
    
        public static void main(String[] args) {
        
            Date currentDate = getCurrentDate();
            System.out.println(currentDate);
            Date firstDayOfMonth = getFirstDayOfMonth(currentDate);
            Date lastDayOfMonth = getLastDayOfMonth(currentDate);
    
            System.out.println("当前日期: " + currentDate);
            System.out.println("本月第一天: " + firstDayOfMonth);
            System.out.println("本月最后一天: " + lastDayOfMonth);
        }
    }

## 2、根据当前日期获取一周的开始和结束日期 ##

import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Calendar;
    import java.util.Date;
    import java.util.function.Function;
    
    /**
     * @Author Mouoal
     * @Description: 说明用途
     * @Date 2023/10/13 15:44
     * @Version 1.0
     */
    public class ddd {
        
        public static class DealWeek {
        
            public static void main(String[] args) throws ParseException {
        
                String date = "20230915";
                Calendar c = getCalendarByDateStr(date);
                System.out.println(c.get(Calendar.WEEK_OF_YEAR));
                String[] result = getStartAndEndDayByDate(date);
                System.out.println("周一日期为：" + result[0]);
                System.out.println("周天日期为：" + result[1]);
            }
    
            //根据日期获取该天所在周的开始与结束日期(周跨年周，只计算本年内那部分天数)
            public static String[] getStartAndEndDayByDate(String yyyyMMdd) throws ParseException{
        
                String[] dateZone = new String[3];
                Calendar cal = getCalendarByDateStr(yyyyMMdd);
                int year = Integer.parseInt(yyyyMMdd.substring(0, 4));
                Function<Integer, String> add0 = (i -> i < 10 ? "0" + i : String.valueOf(i));//补0
    
                dateZone[0] = cal.get(Calendar.YEAR) + add0.apply(cal.get(Calendar.MONTH) + 1)+ add0.apply(cal.get(Calendar.DAY_OF_MONTH));
                if(cal.get(Calendar.YEAR) < year)dateZone[0] = year + "0101";
                cal.add(Calendar.DATE, 6);
                dateZone[1] = cal.get(Calendar.YEAR) +add0.apply(cal.get(Calendar.MONTH) + 1) + add0.apply(cal.get(Calendar.DAY_OF_MONTH));
                if(cal.get(Calendar.YEAR) > year)dateZone[1] = year + "1231";
                dateZone[2] = String.valueOf(cal.get(Calendar.WEEK_OF_YEAR));
                return dateZone;
            }
    
            private static Calendar getCalendarByDateStr(String yyyyMMdd) throws ParseException {
        
                SimpleDateFormat sm = new SimpleDateFormat("yyyyMMdd");
                Date d = sm.parse(yyyyMMdd);
                Calendar cal = Calendar.getInstance();
                cal.setTime(d);
                //判断要计算的日期是否是周日，如果是，则减一天计算周六的，否则会出问题，计算到下一周去了
                int dayWeek = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
                if(1 == dayWeek) cal.add(Calendar.DAY_OF_MONTH, -1);
                cal.setFirstDayOfWeek(Calendar.MONDAY);//设置一个星期的第一天，按中国的习惯一个星期的第一天是星期一
                int day = cal.get(Calendar.DAY_OF_WEEK);//获得当前日期是一个星期的第几天
                cal.add(Calendar.DATE, cal.getFirstDayOfWeek()-day);//根据日历的规则，给当前日期减去星期几与一个星期第一天的差值
                return cal;
            }
    
        }
    }