Java对日期Date类进行加减运算、年份加减月份加减、时间差等等

实现代码一：

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”。

代码二： java date 日期加减天数

测试类代码：

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(); 
   } 
 
}

运行结果：
2014-10-06
2014-10-16
2014-10-06
2014-10-16

代码三：

在网上查阅资料，加上自己总结的一些关于date类的工具类。

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;
 }

目前就用到了这些，随时添加，有简单方便的时间工具类，希望和大家一起学习，在评论中指出。thanks！！！