计算某天是星期几数字或文本形式的JAVA工具方法

柔光的暖阳◎ 2023-07-13 03:04 60阅读 0赞

## 计算某天是星期几数字或文本形式的JAVA工具方法 ##

**1. 代码**

package com.xxx.util;
    
    import java.text.ParseException;
    import java.text.SimpleDateFormat;
    import java.util.Date;
    
    public class DateUtil { 
    
        /** * @param date 日期 * @return 星期几 */
        public static String getWeekday(Date date) { 
            SimpleDateFormat outFormat = new SimpleDateFormat(WEEKDAY_FORMAT);
            return outFormat.format(date);
        }
    
        /** * @param date 日期 * @param format 日期格式 * @return 星期几 */
        public static String getWeekday(String date, String format) { 
            SimpleDateFormat inFormat = new SimpleDateFormat(format);
            Date temp = null;
            try { 
                temp = inFormat.parse(date);
                return getWeekday(temp);
            } catch (ParseException e) { 
                e.printStackTrace();
            }
            return null;
        }
    
    
        public static void main(String[] args) { 
    
            System.out.println(getWeekday(new Date()));
    
            System.out.println(getWeekday("2020-03-11", "yyyy-MM-dd"));
    
            System.out.println(getWeekday("2020/03/19", "yyyy/MM/dd"));
        }
    }

**结果**  
![在这里插入图片描述][20200311101725507.png]

**2. 创建其他格式**

**有些需求不输出数字格式,需要星期一,星期日这种文本格式,或者月份的天数要求.下面摘出JDK自带类SimpleDateFormat和输出格式相关代码和注释.**

package java.text;
    
    /** * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>y</code> * <td>Year * <td><a href="#year">Year</a> * <td><code>1996</code>; <code>96</code> * <tr> * <td><code>Y</code> * <td>Week year * <td><a href="#year">Year</a> * <td><code>2009</code>; <code>09</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>M</code> * <td>Month in year (context sensitive) * <td><a href="#month">Month</a> * <td><code>July</code>; <code>Jul</code>; <code>07</code> * <tr> * <td><code>L</code> * <td>Month in year (standalone form) * <td><a href="#month">Month</a> * <td><code>July</code>; <code>Jul</code>; <code>07</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>w</code> * <td>Week in year * <td><a href="#number">Number</a> * <td><code>27</code> * <tr> * <td><code>W</code> * <td>Week in month * <td><a href="#number">Number</a> * <td><code>2</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>D</code> * <td>Day in year * <td><a href="#number">Number</a> * <td><code>189</code> * <tr> * <td><code>d</code> * <td>Day in month * <td><a href="#number">Number</a> * <td><code>10</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>F</code> * <td>Day of week in month * <td><a href="#number">Number</a> * <td><code>2</code> * <tr> * <td><code>E</code> * <td>Day name in week * <td><a href="#text">Text</a> * <td><code>Tuesday</code>; <code>Tue</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>u</code> * <td>Day number of week (1 = Monday, ..., 7 = Sunday) * <td><a href="#number">Number</a> * <td><code>1</code> * <tr> * <td><code>a</code> * <td>Am/pm marker * <td><a href="#text">Text</a> * <td><code>PM</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>H</code> * <td>Hour in day (0-23) * <td><a href="#number">Number</a> * <td><code>0</code> * <tr> * <td><code>k</code> * <td>Hour in day (1-24) * <td><a href="#number">Number</a> * <td><code>24</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>K</code> * <td>Hour in am/pm (0-11) * <td><a href="#number">Number</a> * <td><code>0</code> * <tr> * <td><code>h</code> * <td>Hour in am/pm (1-12) * <td><a href="#number">Number</a> * <td><code>12</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>m</code> * <td>Minute in hour * <td><a href="#number">Number</a> * <td><code>30</code> * <tr> * <td><code>s</code> * <td>Second in minute * <td><a href="#number">Number</a> * <td><code>55</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>S</code> * <td>Millisecond * <td><a href="#number">Number</a> * <td><code>978</code> * <tr> * <td><code>z</code> * <td>Time zone * <td><a href="#timezone">General time zone</a> * <td><code>Pacific Standard Time</code>; <code>PST</code>; <code>GMT-08:00</code> * <tr style="background-color: rgb(238, 238, 255);"> * <td><code>Z</code> * <td>Time zone * <td><a href="#rfc822timezone">RFC 822 time zone</a> * <td><code>-0800</code> * <tr> * <td><code>X</code> * <td>Time zone * <td><a href="#iso8601timezone">ISO 8601 time zone</a> * <td><code>-08</code>; <code>-0800</code>; <code>-08:00</code> * </table> */
    
    public class SimpleDateFormat extends DateFormat { 
    
        /** * The pattern string of this formatter. This is always a non-localized * pattern. May not be null. See class documentation for details. * @serial */
        private String pattern;
        
        public SimpleDateFormat(String pattern)
        { 
            this(pattern, Locale.getDefault(Locale.Category.FORMAT));
        }
        
        public SimpleDateFormat(String pattern, Locale locale)
        { 
            if (pattern == null || locale == null) { 
                throw new NullPointerException();
            }
    
            initializeCalendar(locale);
            this.pattern = pattern;
            this.formatData = DateFormatSymbols.getInstanceRef(locale);
            this.locale = locale;
            initialize(locale);
        }
    }

**从SimpleDateFormat类的属性pattern的注释和类的注释可以知道,什么字母代表什么含义.例如D代表Day in year,天在年中是第几天,d代表Day in month,天在月中表示第几天.根据自己需要查找需要的格式.**

[20200311101725507.png]: https://img-blog.csdnimg.cn/20200311101725507.png