一、充分利用SimpleDateFormat
import java.text.SimpleDateFormat;import java.util.Calendar;import java.util.Date;public class DateTestUtil {public static void main(String[] args) throws Exception {SimpleDateFormat sdf=new SimpleDateFormat("yyyyMMdd");String str="0823";Date dt=sdf.parse(str);Calendar rightNow = Calendar.getInstance();rightNow.setTime(dt);rightNow.add(Calendar.YEAR,-1);//日期减1年rightNow.add(Calendar.MONTH,3);//日期加3个月rightNow.add(Calendar.DAY_OF_YEAR,10);//日期加10天Date dt1=rightNow.getTime();String reStr = sdf.format(dt1);System.out.println(reStr);}}
注：在Calendar对象的add方法中，第二个参数为正数表示“加”，负数表示“减”。
二、java date 日期加减天数
import java.text.SimpleDateFormat; import java.util.Date; public class DateTest { public static void main(String[] arg){ Date now = new Date(); addAndSubtractDaysByGetTime(now,-5); addAndSubtractDaysByGetTime(now,5); addAndSubtractDaysByCalendar(now,-5); addAndSubtractDaysByCalendar(now,5); } public static Date addAndSubtractDaysByGetTime(Date dateTime/*待处理的日期*/,int n/*加减天数*/){ //日期格式 SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd"); SimpleDateFormat dd=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");System.out.println(df.format(new Date(dateTime.getTime() + n * 24 * 60 * 60 * 1000L))); //System.out.println(dd.format(new Date(dateTime.getTime() + n * 24 * 60 * 60 * 1000L))); //注意这里一定要转换成Long类型，要不n超过25时会出现范围溢出，从而得不到想要的日期值 return new Date(dateTime.getTime() + n * 24 * 60 * 60 * 1000L); } public static Date addAndSubtractDaysByCalendar(Date dateTime/*待处理的日期*/,int n/*加减天数*/){ //日期格式 SimpleDateFormat df=new SimpleDateFormat("yyyy-MM-dd"); SimpleDateFormat dd=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); java.util.Calendar calstart = java.util.Calendar.getInstance(); calstart.setTime(dateTime); calstart.add(java.util.Calendar.DAY_OF_WEEK, n); System.out.println(df.format(calstart.getTime())); //System.out.println(dd.format(calstart.getTime())); return calstart.getTime(); } }
不推荐这个，代码不够简洁，看着不爽。
三、网上找的别人的，太长，没看，粘过来先
package com.data.utils;import java.text.SimpleDateFormat;import java.util.Calendar;import java.util.Date;public class DateFormat {/*** 日期减几年*/public static String dateMinusYear(String str) throws Exception {SimpleDateFormat sdf = new SimpleDateFormat("yyyyMM");Date dt = sdf.parse(str);Calendar rightNow = Calendar.getInstance();rightNow.setTime(dt);rightNow.add(Calendar.YEAR, -1);// 日期减1年Date dt1 = rightNow.getTime();String reStr = sdf.format(dt1);return reStr;}/*** 日期加几年*/public static String dateAddYear(String str) throws Exception {SimpleDateFormat sdf = new SimpleDateFormat("yyyyMM");Date dt = sdf.parse(str);Calendar rightNow = Calendar.getInstance();rightNow.setTime(dt);rightNow.add(Calendar.YEAR, 1);// 日期加1年Date dt1 = rightNow.getTime();String reStr = sdf.format(dt1);return reStr;}/*** 日期减几月*/public static String dateMinusMonth(String str) throws Exception {SimpleDateFormat sdf = new SimpleDateFormat("yyyyMM");Date dt = sdf.parse(str);//将字符串生成DateCalendar rightNow = Calendar.getInstance();rightNow.setTime(dt);//使用给定的 Date 设置此 Calendar 的时间。 rightNow.add(Calendar.MONTH, -1);// 日期减1个月Date dt1 = rightNow.getTime();//返回一个表示此 Calendar 时间值的 Date 对象。String reStr = sdf.format(dt1);//将给定的 Date 格式化为日期/时间字符串，并将结果添加到给定的 StringBuffer。return reStr;}/*** 日期加几月*/public static String dateAddMonth(String str) throws Exception {SimpleDateFormat sdf = new SimpleDateFormat("yyyyMM");Date dt = sdf.parse(str);Calendar rightNow = Calendar.getInstance();rightNow.setTime(dt);rightNow.add(Calendar.MONTH, 1);// 日期加3个月// rightNow.add(Calendar.DAY_OF_YEAR,10);//日期加10天Date dt1 = rightNow.getTime();String reStr = sdf.format(dt1);return reStr;}/*** 获取当前年月的第一个月的str** @param str 05* @return 01* @throws Exception*/public static String dateOneMonth(String str) {str = str.substring(0, str.length() - 2);str = str + "01";return str;}/*** 算出所选月份距离一月份有几个月。** @param str 09* @return 9*/public static int dateDistanceMonth(String str) {int i = Integer.parseInt(str);int j = Integer.parseInt(DateFormat.dateOneMonth(str));System.out.println(i - j);return i - j + 1;}/*** 获取两个时间的时间差，精确到毫秒** @param str* @return*/public static String TimeDifference(long start, long end) {long between = end - start;long day = between / (24 * 60 * 60 * 1000);long hour = (between / (60 * 60 * 1000) - day * 24);long min = ((between / (60 * 1000)) - day * 24 * 60 - hour * 60);long s = (between / 1000 - day * 24 * 60 * 60 - hour * 60 * 60 - min * 60);long ms = (between - day * 24 * 60 * 60 * 1000 - hour * 60 * 60 * 1000- min * 60 * 1000 - s * 1000);String timeDifference = day + "天" + hour + "小时" + min + "分" + s + "秒" + ms+ "毫秒";return timeDifference;}}/*** 获取24小时、一周、一个月的起始时间** @param timeInterval : DAY_TIME_INTERVAL WEEK_TIME_INTERVAL MONTH_TIME_INTERVAL* @return "yyyy-mm-dd hh:mm:ss"*/public static String getStartTime(int timeInterval) {Calendar cal = Calendar.getInstance();SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");if (DAY_TIME_INTERVAL == timeInterval) {// 获取24小时的起始时间cal.set(Calendar.HOUR_OF_DAY, 0);cal.set(Calendar.MINUTE, 0);cal.set(Calendar.SECOND, 0);String startTime = sdf.format(cal.getTime());return startTime;} else if (WEEK_TIME_INTERVAL == timeInterval) {int weekday = cal.get(Calendar.DAY_OF_WEEK) - 1;cal.add(Calendar.DATE, -weekday);cal.set(Calendar.HOUR_OF_DAY, 0);cal.set(Calendar.MINUTE, 0);cal.set(Calendar.SECOND, 0);String startTime = sdf.format(cal.getTime());return startTime;} else if (MONTH_TIME_INTERVAL == timeInterval) {int dayofmonthMin = cal.getActualMinimum(Calendar.DAY_OF_MONTH);// c.add(Calendar.DATE, -dayofmonth);cal.set(Calendar.DATE, dayofmonthMin);cal.set(Calendar.HOUR_OF_DAY, 0);cal.set(Calendar.MINUTE, 0);cal.set(Calendar.SECOND, 0);String startTime = sdf.format(cal.getTime());return startTime;}return null;}/*** 获取24小时、一周、一个月的结束时间** @param timeInterval : DAY_TIME_INTERVAL WEEK_TIME_INTERVAL MONTH_TIME_INTERVAL* @return "yyyy-mm-dd hh:mm:ss"*/public static String getEndTime(int timeInterval) {Calendar cal = Calendar.getInstance();cal.setTimeZone(TimeZone.getTimeZone("GMT+8"));SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");if (DAY_TIME_INTERVAL == timeInterval) {cal.set(Calendar.HOUR_OF_DAY, 23);cal.set(12, 59);cal.set(13, 59);long date = cal.getTimeInMillis();String endTime = sdf.format(new Date(date));return endTime;} else if (WEEK_TIME_INTERVAL == timeInterval) {int weekday = cal.get(Calendar.DAY_OF_WEEK) - 1;cal.add(Calendar.DATE, -weekday);cal.add(Calendar.DATE, 6);cal.set(Calendar.HOUR_OF_DAY, 23);cal.set(12, 59);cal.set(13, 59);long date = cal.getTimeInMillis();String endTime = sdf.format(new Date(date));return endTime;} else if (MONTH_TIME_INTERVAL == timeInterval) {int dayOfMonthMax = cal.getActualMaximum(Calendar.DAY_OF_MONTH);cal.set(Calendar.DATE, dayOfMonthMax);cal.set(Calendar.HOUR_OF_DAY, 23);cal.set(Calendar.MINUTE, 59);cal.set(Calendar.SECOND, 59);String endTime = sdf.format(cal.getTime());return endTime;}return null;}/*** 判断dateStr是否在start和end中间，start和end都可以为null yyyyMMddHHmmss或者yyyyMMdd格式** @param dateStr* @param start* @param end* @return* @author you.xu* @date 8月19日下午3:11:46*/public static boolean checkDateVal(String dateStr, String start, String end) {boolean isDateRight = false;Date date = null;Date startDate = null;Date endDate = null;SimpleDateFormat sdf = null;// 判断日期格式if (14 == dateStr.length()) {sdf = new SimpleDateFormat("yyyyMMddHHmmss");} else if (8 == dateStr.length()) {sdf = new SimpleDateFormat("yyyyMMdd");} elsereturn false;try {// 更改判断日期格式date = sdf.parse(dateStr);} catch (ParseException e) {log.error(e, e);}if ((start == null) && (end != null)) {try {endDate = sdf.parse(end);} catch (ParseException ex1) {log.error(ex1, ex1);}if ((date != null) && (endDate != null))// Check parameters for{if (pareTo(endDate) <= 0)isDateRight = true;}} else if ((start != null) && (end == null)) {try {startDate = sdf.parse(start);} catch (ParseException ex1) {log.error(ex1, ex1);}if ((date != null) && (startDate != null)) {if (pareTo(startDate) >= 0)isDateRight = true;}} else if ((start != null) && (end != null)) {try {startDate = sdf.parse(start);endDate = sdf.parse(end);} catch (ParseException ex2) {System.out.println(ex2.toString());}if ((startDate != null) && (date != null) && (endDate != null)) {if ((pareTo(startDate) >= 0)&& (pareTo(endDate) <= 0))isDateRight = true;}}return isDateRight;}/*** 判断dateStr是否在start和end中间，start和end都可以为null long形格式** @param dateStr* @param start* @param end* @return* @author you.xu* @date 8月19日下午3:12:35*/public static boolean checkDateV(String dateStr, String start, String end) {boolean isDateRight = false;long date = -1;long fromDate = -1;long toDate = -1;date = java.lang.Long.parseLong(dateStr);if ((start == null) && (end == null)) {isDateRight = true;} else if ((start == null) && (end != null)) {try {toDate = java.lang.Long.parseLong(end);} catch (NumberFormatException nfe) {log.error(nfe, nfe);}if (date <= toDate) {isDateRight = true;}} else if ((start != null) && (end == null)) {try {fromDate = java.lang.Long.parseLong(start);} catch (NumberFormatException nfe) {log.error(nfe, nfe);}if (date >= fromDate) {isDateRight = true;}} else if ((start != null) && (end != null)) {try {toDate = java.lang.Long.parseLong(end);fromDate = java.lang.Long.parseLong(start);} catch (NumberFormatException nfe) {log.error(nfe, nfe);}if ((date <= toDate) && (date >= fromDate)) {isDateRight = true;}}return isDateRight;}
四、自己的方法的，简单说下需求，由于数据库里的存储类型是 “-07-04 12：00：00”，要按当前时间向前检索传进来的天数（noTradeDays），利用java.util的GregorianCalendar，结合SimpleDateFormat，完成当前时间逆推的需求
/*** add by lee /7/4 * 连续n天无交易*/if (!StringUtils.isEmpty(noTradeDays)) {**SimpleDateFormat sdf=new SimpleDateFormat("yyyy-MM-dd HH:mm:ss");GregorianCalendar gc=new GregorianCalendar(); gc.setTime(new Date());gc.add(5, -Integer.parseInt(noTradeDays));**String cardSql="select posid from card where usetime between "+"'"+sdf.format(gc.getTime())+"'"+" and "+"'"+sdf.format(new Date())+"'"+" group by posid";List<Card> cards = CardService.cardDAO.executeQuery(new Query(cardSql));if (cards.size()>0) {StringBuffer sb=new StringBuffer();for (Card posId : cards) {if (!StringUtils.isEmpty(posId.getPosid())) {sb.append("'").append(posId.getPosid()).append("'").append(",");}}if (sb.length()>0) {sql_add +=" and posid not in ("+sb.substring(0, sb.length()-1).toString()+")";}}}
恩，就是这样子了，总之就是灵活运用java.util里关于日期的相关类。
出处：
Java对日期Date类进行加减运算一二三_hacker_Lees的博客-CSDN博客_date加减日期
