【Java】工具|日期处理

1、当月有多少天

1&＃xff09;maven依赖

org.apache.commonscommons-lang3


2&＃xff09;java方法

/**
* 当月有多少天
* &＃64;param month 月份&＃xff0c;eg:2021-09,2021-09-22
* &＃64;return
*/
public static int getTotalDayOfMonth(String month) {Date date &＃61; DateUtils.parseDate(month);Calendar calendar &＃61; Calendar.getInstance();calendar.setTime(date);calendar.set(Calendar.DAY_OF_MONTH, calendar.getActualMaximum(Calendar.DAY_OF_MONTH));SimpleDateFormat sdf &＃61; new SimpleDateFormat("dd");String lastDay &＃61; sdf.format(calendar.getTime());return Integer.parseInt(lastDay);
}

2、获取两日期之间的月份以及每月对应的天数

1&＃xff09;结果示例

 2&＃xff09;java代码

/*** 两日期之间的月份与天数* &＃64;param dateStart YYYYMMDD* &＃64;param dateEnd YYYYMMDD dateEnd需大于dateStart* &＃64;return key: YYYYMM,val:天数*/public static Map betweenDay(String dateStart, String dateEnd) {Map dataMap &＃61; MapUtil.newHashMap();String firstMonth &＃61; getYearAndMonth(dateStart);int firstMonthDay &＃61; getDayInt(dateStart);int firstMonthTotalDay &＃61; getTotalDayOfMonth(dateStart);// 开始月&＃xff0c;剩余多少天int firstMonthBetweenDay &＃61; firstMonthTotalDay - firstMonthDay &＃43; 1;dataMap.put(firstMonth, firstMonthBetweenDay);// 最后一个月String lastMonth &＃61; getYearAndMonth(dateEnd);// 最后一个月&＃xff0c;间隔多少天int lastMonthBetweenDay &＃61; getDayInt(dateEnd);dataMap.put(lastMonth, lastMonthBetweenDay);String tmpYear &＃61; null;String tmpMonth &＃61; null;int tmpMonthInt &＃61; 0;int tmpYearInt &＃61; 0;int monthTotal &＃61; 12;int daysNum &＃61; 0;for (String tmpDate &＃61; firstMonth; tmpDate.compareTo(lastMonth) <0;) {tmpYear &＃61; getYear(tmpDate);tmpYearInt &＃61; Integer.parseInt(tmpYear);tmpMonth &＃61; getMonth(tmpDate);tmpMonthInt &＃61; Integer.parseInt(tmpMonth);tmpMonthInt&＃43;&＃43;;if (tmpMonthInt > monthTotal) {tmpYearInt&＃43;&＃43;;tmpMonthInt %&＃61; monthTotal;}tmpDate &＃61; tmpYearInt &＃43; formatMonth(tmpMonthInt);if (tmpDate.compareTo(lastMonth) >&＃61; 0) {break;}daysNum &＃61; getTotalDayOfMonth(tmpDate);dataMap.put(tmpDate, daysNum);}return dataMap;}

3&＃xff09;其他依赖

/*** 获取年* &＃64;param date YYYYMMDD* &＃64;return YYYY*/public static String getYear(String date) {date &＃61; StringUtils.val(date).replaceAll("-", "");if (date.length() > 3) {return date.substring(0, 4);}return date;}/*** 获取月* &＃64;param date YYYYMMDD* &＃64;return MM*/public static String getMonth(String date) {date &＃61; StringUtils.val(date).replaceAll("-", "");if (date.length() > 5) {return date.substring(4, 6);}return date;}/*** 获取日* &＃64;param date YYYYMMDD* &＃64;return MM*/public static String getDay(String date) {date &＃61; StringUtils.val(date).replaceAll("-", "");int length &＃61; date.length();return date.substring(6, length);}/*** 获取日* &＃64;param date YYYYMMDD* &＃64;return*/public static int getDayInt(String date) {return Integer.parseInt(getDay(date));}/*** 获取年月* &＃64;param date YYYYMMDD* &＃64;return YYYYMM*/public static String getYearAndMonth(String date) {return getYear(date) &＃43; getMonth(date);}/*** 格式化月* &＃64;param month 1* &＃64;return 01*/public static String formatMonth(int month) {return String.format("%02d", month);}