java获取当天是周几

╰半夏微凉° 2022-11-15 01:26 245阅读 0赞

### java获取当天是周几 ###

#### 方式说明 ####

*  用Calendar\#DAY\_OF\_WEEK 来获取
 *  用SimpleDateFormat 的 `u` 周标识,格式化日期来获取
 *  用LocalDate.getDayOfWeek() 来获取

#### 代码实现 ####

package com.example.demo.util.date;
    
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.time.DayOfWeek;
    import java.time.LocalDate;
    import java.time.ZoneId;
    import java.time.format.DateTimeFormatter;
    import java.time.temporal.ChronoField;
    import java.util.Calendar;
    import java.util.Date;
    import java.util.TimeZone;
    
    /** * 获得当前周几 */
    public class DateUtils { 
    
        public static void main(String[] args) throws ParseException { 
            getWeekFromStrDateByCalendar("2021-03-28");
            getWeekFormStrDateByFormat("2021-03-28");
            getWeekFromStrDateByLocalDate("2021-03-28");
        }
    
    
        static SimpleDateFormat simpleDateFormat = new SimpleDateFormat("yyyy-MM-dd");
        static DateTimeFormatter formatter = DateTimeFormatter.ofPattern("yyyy-MM-dd");
    
        /** * @see java.util.Calendar#DAY_OF_WEEK * @see java.util.Calendar#SUNDAY * Calendar 对象中 周日开始的 标识 1, 周六 标识 7 * 将对象转为 Calendar 对象,在用该对象的 get 方法,带入指定字段获取 对应的 值 (DAY_OF_WEEK) * @param str * @throws ParseException */
        public static void getWeekFromStrDateByCalendar(String str) throws ParseException { 
            Date parse = simpleDateFormat.parse(str);
            Calendar instance = Calendar.getInstance(TimeZone.getTimeZone(ZoneId.of("Asia/Shanghai")));
            instance.setTime(parse);
            int i = instance.get(Calendar.DAY_OF_WEEK);
            System.out.println(i);
        }
    
        /** * 根据 SimpleDateFormat 对象的 说明,提示,发送 周几 对应的格式符 为 'u' * @param str * @throws ParseException */
        public static void getWeekFormStrDateByFormat(String str) throws ParseException { 
            Date parse = simpleDateFormat.parse(str);
            // u 指定周几
            SimpleDateFormat format = new SimpleDateFormat("u");
            String format1 = format.format(parse);
            System.out.println(format1);
        }
    
    
    
    
        /** * @param str * @throws ParseException */
        public static void getWeekFromStrDateByLocalDate(String str) throws ParseException { 
            LocalDate parse = LocalDate.parse(str, formatter);
            DayOfWeek dayOfWeek = parse.getDayOfWeek();
            System.out.println(dayOfWeek.toString());
            System.out.println(dayOfWeek.get(ChronoField.DAY_OF_WEEK));
        }
    
    
    }