Java对日期Date类进行加减运算一二三

废话不多 ，代码说话：

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="20110823";
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Date
Calendar 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
*   201505
* @return 201501
* @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 201509
* @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
*
* @author you.xu
* @date 2015年8月19日下午3:11:46
* @param dateStr
* @param start
* @param end
* @return
*/
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");
} else
return 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 (date.compareTo(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 (date.compareTo(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 ((date.compareTo(startDate) >= 0)
&& (date.compareTo(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
*
* @author you.xu
* @date 2015年8月19日下午3:12:35
* @param dateStr
* @param start
* @param end
* @return
*/
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 “2017-07-04 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 2017/7/4
* 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。