关于Java日期工具类的编写

Date date = simpleDateFormat.parse(string);  

String string = simpleDateFormat.format(date);  

public static void main(String[] args) throws ParseException { //统一日期格式 String StrVal = "2018年05月22日"; Date d1 = new SimpleDateFormat("yyyy年MM月dd日").parse(StrVal); SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd"); String time = format.format(d1); System.out.println(time); }

    /** * 将日期对象格式化为指定格式的日期字符串 * @param date 传入的日期对象 * @param format 格式 * @return */ public static String formatDate(Date date,String format){ String result=""; SimpleDateFormat sdf=new SimpleDateFormat(format); if(date!=null){ result=sdf.format(date); } return result; } /** * 将日期字符串转换成一个日期对象 * @param dateStr 日期字符串 * @param format 格式 * @return * @throws ParseException */ public static Date formatDate(String dateStr,String format) throws ParseException{ SimpleDateFormat sdf=new SimpleDateFormat(format); return sdf.parse(dateStr); } public static void main(String[] args) throws ParseException { Date date=new Date(); System.out.println(formatDate(date,"yyyy-MM-dd")); System.out.println(formatDate(date,"yyyy-MM-dd HH:mm:ss")); System.out.println(formatDate(date,"yyyy年MM月dd日HH时mm分ss秒")); String dataStr="1989-11-02 18:01:41"; Date date2=formatDate(dataStr,"yyyy-MM-dd HH:mm:ss"); System.out.println(formatDate(date2,"yyyy-MM-dd HH:mm:ss")); }

    public static void main(String[] args) { //默认输出格式 Date date=new Date(); System.out.println(date); //日期格式化显示，首先定义格式 SimpleDateFormat sdf1=new SimpleDateFormat("yyyyMMdd"); SimpleDateFormat sdf2=new SimpleDateFormat("yyyy-MM-dd"); SimpleDateFormat sdf3=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); SimpleDateFormat sdf4=new SimpleDateFormat("yyyy年MM月dd日HH时mm分ss秒"); //将格式应用于日期 System.out.println(sdf1.format(date)); System.out.println(sdf2.format(date)); System.out.println(sdf3.format(date)); System.out.println(sdf4.format(date)); }

import java.util.Calendar; public class Test { public static void main(String[] args) { String[] weekDays = {"星期日", "星期一", "星期二", "星期三", "星期四", "星期五", "星期六"}; Calendar calendar=Calendar.getInstance(); System.out.println("今天是"+weekDays[calendar.get(Calendar.DAY_OF_WEEK)-1]); } }

    public static void main(String[] args) { //默认输出格式 Date now = new Date(); SimpleDateFormat format = new SimpleDateFormat("yyyy-MM-dd"); String time = format.format(now); System.out.println(time); Calendar calendar = Calendar.getInstance(); calendar.setTime(now); calendar.add(Calendar.MONTH, 1); SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); String nowTime = sdf.format(calendar.getTime()); System.out.println(nowTime); calendar.add(Calendar.MONTH, -2); String nowTime2 = sdf.format(calendar.getTime()); System.out.println(nowTime2); }

    public static void main(String[] args) { //默认输出格式 Date now = new Date(); SimpleDateFormat nowSdf = new SimpleDateFormat("yyyy-MM-dd"); System.out.println(nowSdf.format(now)); Calendar calendar = Calendar.getInstance(); // 赋值时年月日时分秒常用的6个值，注意月份下标从0开始，所以取月份要+1 System.out.println("年:" + calendar.get(Calendar.YEAR)); System.out.println("月:" + (calendar.get(Calendar.MONTH) + 1)); System.out.println("日:" + calendar.get(Calendar.DAY_OF_MONTH)); System.out.println("时:" + calendar.get(Calendar.HOUR_OF_DAY)); System.out.println("分:" + calendar.get(Calendar.MINUTE)); System.out.println("秒:" + calendar.get(Calendar.SECOND)); SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); String nowTime2 = sdf.format(calendar.getTime()); System.out.println(nowTime2); }

    public static void main(String[] args) { //默认输出格式 Date now = new Date(); SimpleDateFormat nowSdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); System.out.println(nowSdf.format(now)); Calendar calendar = Calendar.getInstance(); calendar.set(2013, 5, 4, 13, 44, 51); calendar.set(Calendar.YEAR, 2014);//年 SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); String nowTime = sdf.format(calendar.getTime()); System.out.println(nowTime); calendar.set(Calendar.MONTH, 7);//月（月份0代表1月） SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); String nowTime1 = sdf1.format(calendar.getTime()); System.out.println(nowTime1); calendar.set(Calendar.DATE, 11);//日 calendar.set(Calendar.HOUR_OF_DAY, 15);//时 calendar.set(Calendar.MINUTE, 33);//分 calendar.set(Calendar.SECOND, 32);//秒 }

    public static void main(String[] args) { //默认输出格式 Date now = new Date(); SimpleDateFormat nowSdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); System.out.println(nowSdf.format(now)); Calendar calendar = Calendar.getInstance(); calendar.setTime(now); calendar.add(Calendar.YEAR, 1);//年 calendar.add(Calendar.MONTH, 1);//月 calendar.add(Calendar.DATE, 1);//日 //calendar.add(Calendar.DAY_OF_YEAR, 1);//今年的第 N 天 //calendar.add(Calendar.DAY_OF_MONTH, 1); // 本月第 N 天 //calendar.add(Calendar.DAY_OF_WEEK, 1);// 本周几 calendar.add(Calendar.HOUR_OF_DAY, -1);//时 calendar.add(Calendar.MINUTE, 1);//分 calendar.add(Calendar.SECOND, 1);//秒 //calendar.add(calendar.WEEK_OF_MONTH, 1);//增加一个礼拜 //calendar.add(calendar.WEEK_OF_YEAR,1);//增加一个礼拜 SimpleDateFormat sdf1 = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); String nowTime1 = sdf1.format(calendar.getTime()); System.out.println(nowTime1); }

    public static void main(String[] args) { //默认输出格式 Date now = new Date(); SimpleDateFormat nowSdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); Calendar calendar = Calendar.getInstance(); int firstD = calendar.getActualMinimum(calendar.DAY_OF_MONTH); int lastD = calendar.getActualMaximum(calendar.DAY_OF_MONTH); System.out.println("获取本月的第一天和最后天：" + firstD +"," + lastD); }

    public static Date geLastWeekMonday(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(getThisWeekMonday(date)); cal.add(Calendar.DATE, -7); return cal.getTime(); } public static Date getThisWeekMonday(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(date); // 获得当前日期是一个星期的第几天 int dayWeek = cal.get(Calendar.DAY_OF_WEEK); if (1 == dayWeek) { cal.add(Calendar.DAY_OF_MONTH, -1); } // 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 cal.setFirstDayOfWeek(Calendar.MONDAY); // 获得当前日期是一个星期的第几天 int day = cal.get(Calendar.DAY_OF_WEEK); // 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 cal.add(Calendar.DATE, cal.getFirstDayOfWeek() - day); return cal.getTime(); } public static Date getNextWeekMonday(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(getThisWeekMonday(date)); cal.add(Calendar.DATE, 7); return cal.getTime(); } public static void main(String[] args) { SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd"); try { Date date = sdf.parse("2017-09-10"); System.out.println("今天是" + sdf.format(date)); System.out.println("上周一" + sdf.format(geLastWeekMonday(date))); System.out.println("本周一" + sdf.format(getThisWeekMonday(date))); System.out.println("下周一" + sdf.format(getNextWeekMonday(date))); } catch (Exception e) { e.printStackTrace(); } }

public static void main(String[] args) { Calendar love = Calendar.getInstance(); Calendar now = Calendar.getInstance(); love.set(2016, 8, 6); //真实的日期是2016-9-6; int days = (int) ((now.getTimeInMillis() - love.getTimeInMillis()) / (24 * 60 * 60 * 1000.0)); System.out.println(days); }

public static void main(String[] args) throws ParseException { SimpleDateFormat format=new SimpleDateFormat("yyyy-MM-dd");//大小写还是很重要的 Date LoveDay=new Date(); Date now=new Date(); LoveDay=format.parse("2016-08-06"); int day=(int) ((now.getTime()-LoveDay.getTime())/(24*60*60*1000)); System.out.println(day); }

 import java.text.ParseException; import java.text.SimpleDateFormat; import java.util.Calendar; import java.util.Date; public class DateUtils { public static final String DATE_TIME_PATTERN = "yyyy-MM-dd HH:mm:ss"; public static final String MINUTE_PATTERN = "yyyy-MM-dd HH:mm"; public static final String HOUR_PATTERN = "yyyy-MM-dd HH:mm:ss"; public static final String DATE_PATTERN = "yyyy-MM-dd"; public static final String MONTH_PATTERN = "yyyy-MM"; public static final String YEAR_PATTERN = "yyyy"; public static final String MINUTE_ONLY_PATTERN = "mm"; public static final String HOUR_ONLY_PATTERN = "HH"; /** * 日期相加减天数 * @param date 如果为Null，则为当前时间 * @param days 加减天数 * @param includeTime 是否包括时分秒,true表示包含 * @return * @throws ParseException */ public static Date dateAdd(Date date, int days, boolean includeTime) throws ParseException{ if(date == null){ date = new Date(); } if(!includeTime){ SimpleDateFormat sdf = new SimpleDateFormat(DateUtils.DATE_PATTERN); date = sdf.parse(sdf.format(date)); } Calendar cal = Calendar.getInstance(); cal.setTime(date); cal.add(Calendar.DATE, days); return cal.getTime(); } /** * 时间格式化成字符串 * @param date Date * @param pattern StrUtils.DATE_TIME_PATTERN || StrUtils.DATE_PATTERN， 如果为空，则为yyyy-MM-dd * @return * @throws ParseException */ public static String dateFormat(Date date, String pattern) throws ParseException{ if(pattern==null||pattern.length()==0||pattern.equals(" ")){ pattern = DateUtils.DATE_PATTERN; } SimpleDateFormat sdf = new SimpleDateFormat(pattern); return sdf.format(date); } /** * 字符串解析成时间对象 * @param dateTimeString String * @param pattern StrUtils.DATE_TIME_PATTERN || StrUtils.DATE_PATTERN，如果为空，则为yyyy-MM-dd * @return * @throws ParseException */ public static Date dateParse(String dateTimeString, String pattern) throws ParseException{ if(pattern==null||pattern.length()==0||pattern.equals(" ")){ pattern = DateUtils.DATE_PATTERN; } SimpleDateFormat sdf = new SimpleDateFormat(pattern); return sdf.parse(dateTimeString); } /** * 将日期时间格式成只有日期的字符串（可以直接使用dateFormat，Pattern为Null进行格式化） * @param dateTime Date * @return * @throws ParseException */ public static String dateTimeToDateString(Date dateTime) throws ParseException{ String dateTimeString = DateUtils.dateFormat(dateTime, DateUtils.DATE_TIME_PATTERN); return dateTimeString.substring(0, 10); } /** * 当时、分、秒为00:00:00时，将日期时间格式成只有日期的字符串， * 当时、分、秒不为00:00:00时，直接返回 * @param dateTime Date * @return * @throws ParseException */ public static String dateTimeToDateStringIfTimeEndZero(Date dateTime) throws ParseException{ String dateTimeString = DateUtils.dateFormat(dateTime, DateUtils.DATE_TIME_PATTERN); if(dateTimeString.endsWith("00:00:00")){ return dateTimeString.substring(0, 10); }else{ return dateTimeString; } } /** * 将日期时间格式成日期对象，和dateParse互用 * @param dateTime Date * @return Date * @throws ParseException */ public static Date dateTimeToDate(Date dateTime) throws ParseException{ Calendar cal = Calendar.getInstance(); cal.setTime(dateTime); cal.set(Calendar.HOUR_OF_DAY, 0); cal.set(Calendar.MINUTE, 0); cal.set(Calendar.SECOND, 0); cal.set(Calendar.MILLISECOND, 0); return cal.getTime(); } /** * 时间加减小时 * @param startDate 要处理的时间，Null则为当前时间 * @param hours 加减的小时 * @return Date */ public static Date dateAddHours(Date startDate, int hours) { if (startDate == null) { startDate = new Date(); } Calendar c = Calendar.getInstance(); c.setTime(startDate); c.set(Calendar.HOUR, c.get(Calendar.HOUR) + hours); return c.getTime(); } /** * 时间加减分钟 * @param startDate 要处理的时间，Null则为当前时间 * @param minutes 加减的分钟 * @return */ public static Date dateAddMinutes(Date startDate, int minutes) { if (startDate == null) { startDate = new Date(); } Calendar c = Calendar.getInstance(); c.setTime(startDate); c.set(Calendar.MINUTE, c.get(Calendar.MINUTE) + minutes); return c.getTime(); } /** * 时间加减秒数 * @param startDate 要处理的时间，Null则为当前时间 * @param minutes 加减的秒数 * @return */ public static Date dateAddSeconds(Date startDate, int seconds) { if (startDate == null) { startDate = new Date(); } Calendar c = Calendar.getInstance(); c.setTime(startDate); c.set(Calendar.SECOND, c.get(Calendar.SECOND) + seconds); return c.getTime(); } /** * 时间加减天数 * @param startDate 要处理的时间，Null则为当前时间 * @param days 加减的天数 * @return Date */ public static Date dateAddDays(Date startDate, int days) { if (startDate == null) { startDate = new Date(); } Calendar c = Calendar.getInstance(); c.setTime(startDate); c.set(Calendar.DATE, c.get(Calendar.DATE) + days); return c.getTime(); } /** * 时间加减月数 * @param startDate 要处理的时间，Null则为当前时间 * @param months 加减的月数 * @return Date */ public static Date dateAddMonths(Date startDate, int months) { if (startDate == null) { startDate = new Date(); } Calendar c = Calendar.getInstance(); c.setTime(startDate); c.set(Calendar.MONTH, c.get(Calendar.MONTH) + months); return c.getTime(); } /** * 时间加减年数 * @param startDate 要处理的时间，Null则为当前时间 * @param years 加减的年数 * @return Date */ public static Date dateAddYears(Date startDate, int years) { if (startDate == null) { startDate = new Date(); } Calendar c = Calendar.getInstance(); c.setTime(startDate); c.set(Calendar.YEAR, c.get(Calendar.YEAR) + years); return c.getTime(); } /** * 时间比较（如果myDate>compareDate返回1，<返回-1，相等返回0） * @param myDate 时间 * @param compareDate 要比较的时间 * @return int */ public static int dateCompare(Date myDate, Date compareDate) { Calendar myCal = Calendar.getInstance(); Calendar compareCal = Calendar.getInstance(); myCal.setTime(myDate); compareCal.setTime(compareDate); return myCal.compareTo(compareCal); } /** * 获取两个时间中最小的一个时间 * @param date * @param compareDate * @return */ public static Date dateMin(Date date, Date compareDate) { if(date == null){ return compareDate; } if(compareDate == null){ return date; } if(1 == dateCompare(date, compareDate)){ return compareDate; }else if(-1 == dateCompare(date, compareDate)){ return date; } return date; } /** * 获取两个时间中最大的一个时间 * @param date * @param compareDate * @return */ public static Date dateMax(Date date, Date compareDate) { if(date == null){ return compareDate; } if(compareDate == null){ return date; } if(1 == dateCompare(date, compareDate)){ return date; }else if(-1 == dateCompare(date, compareDate)){ return compareDate; } return date; } /** * 获取两个日期（不含时分秒）相差的天数，不包含今天 * @param startDate * @param endDate * @return * @throws ParseException */ public static int dateBetween(Date startDate, Date endDate) throws ParseException { Date dateStart = dateParse(dateFormat(startDate, DATE_PATTERN), DATE_PATTERN); Date dateEnd = dateParse(dateFormat(endDate, DATE_PATTERN), DATE_PATTERN); return (int) ((dateEnd.getTime() - dateStart.getTime())/1000/60/60/24); } /** * 获取两个日期（不含时分秒）相差的天数，包含今天 * @param startDate * @param endDate * @return * @throws ParseException */ public static int dateBetweenIncludeToday(Date startDate, Date endDate) throws ParseException { return dateBetween(startDate, endDate) + 1; } /** * 获取日期时间的年份，如2017-02-13，返回2017 * @param date * @return */ public static int getYear(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(date); return cal.get(Calendar.YEAR); } /** * 获取日期时间的月份，如2017年2月13日，返回2 * @param date * @return */ public static int getMonth(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(date); return cal.get(Calendar.MONTH) + 1; } /** * 获取日期时间的第几天（即返回日期的dd），如2017-02-13，返回13 * @param date * @return */ public static int getDate(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(date); return cal.get(Calendar.DATE); } /** * 获取日期时间当月的总天数，如2017-02-13，返回28 * @param date * @return */ public static int getDaysOfMonth(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(date); return cal.getActualMaximum(Calendar.DATE); } /** * 获取日期时间当年的总天数，如2017-02-13，返回2017年的总天数 * @param date * @return */ public static int getDaysOfYear(Date date) { Calendar cal = Calendar.getInstance(); cal.setTime(date); return cal.getActualMaximum(Calendar.DAY_OF_YEAR); } /** * 根据时间获取当月最大的日期 * 
2017-02-13，返回2017-02-28
 * 
2016-02-13，返回2016-02-29
 * 
2016-01-11，返回2016-01-31
 * @param date Date * @return * @throws Exception */ public static Date maxDateOfMonth(Date date) throws Exception { Calendar cal = Calendar.getInstance(); cal.setTime(date); int value = cal.getActualMaximum(Calendar.DATE); return dateParse(dateFormat(date, MONTH_PATTERN) + "-" + value, null); } /** * 根据时间获取当月最小的日期，也就是返回当月的1号日期对象 * @param date Date * @return * @throws Exception */ public static Date minDateOfMonth(Date date) throws Exception { Calendar cal = Calendar.getInstance(); cal.setTime(date); int value = cal.getActualMinimum(Calendar.DATE); return dateParse(dateFormat(date, MONTH_PATTERN) + "-" + value, null); } }

   public static void main(String[] args) throws Exception { System.out.println(dateTimeToDate(new Date())); System.out.println(dateParse("2017-02-04 14:58:20", null)); System.out.println(dateTimeToDateStringIfTimeEndZero(new Date())); System.out.println(dateTimeToDateStringIfTimeEndZero(dateTimeToDate(new Date()))); System.out.println(dateBetween(dateParse("2017-01-30", null), dateParse("2017-02-01", null))); System.out.println(dateBetweenIncludeToday(dateParse("2017-01-30", null), dateParse("2017-02-01", null))); System.out.println(getDate(dateParse("2017-01-17", null))); System.out.println(getDaysOfMonth(dateParse("2017-02-01", null))); System.out.println(getDaysOfYear(dateParse("2017-01-30", null))); /*   System.out.println(dateFormat(dateAddMonths(dateParse("2017-02-07", StrUtils.MONTH_PATTERN), -12), StrUtils.MONTH_PATTERN));*/ System.out.println(dateFormat(maxDateOfMonth(dateParse("2016-02", "yyyy-MM")), null)); System.out.println(dateFormat(minDateOfMonth(dateParse("2016-03-31", null)), null)); }