两个日期相减

在项目中经常遇到日期相减的业务，一下是几种日期想减的代码集合，希望对各位有帮助！
1.SimpleDateFormat myFormatter = new SimpleDateFormat("yyyy-MM-dd");
  java.util.Date date= myFormatter.parse("2003-05-1"); 
  java.util.Date mydate= myFormatter.parse("1899-12-30");
  long  day=(date.getTime()-mydate.getTime())/(24*60*60*1000);




2. public int daysOfTwoDate(Date beginDate,Date endDate){ 
          int days = 0;//两个日期之前的天数 
            DateFormat df = new SimpleDateFormat("yyyy-MM-dd HH:mm:ss"); 
 
          Calendar beginCalendar = Calendar.getInstance(); 
          Calendar endCalendar = Calendar.getInstance(); 
           
          beginCalendar.setTime(beginDate); 
          endCalendar.setTime(endDate); 
          //计算天数 
          while(beginCalendar.before(endCalendar)){ 
              days++; 
              beginCalendar.add(Calendar.DAY_OF_MONTH, 1); 
          } 
          return days; 





3.
import java.util.*;
import java.text.*;
public class TestTime{
static int day=0;
static long d=0,l=0;
public static void main(String [] args){
long day=0;
TestTime a=new TestTime();
try{
day=(int)a.getCompareDate();

}catch(Exception se){
se.printStackTrace();
}
int ten=(int)day/10;
int gen=(int)day%10;

System.out.println(gen+"aa"+ten+"bb"+day);

}
public static long getCompareDate(){
Calendar cal = Calendar.getInstance();
//当前年月日
int year=cal.get(Calendar.YEAR);
int month=cal.get(Calendar.MONTH);
int date=cal.get(Calendar.DATE);
//System.out.println("年"+year+"月"+month+"日"+date);

cal.set(year, month, date);
Date date1=cal.getTime();
cal.set(2008,Calendar.AUGUST,8);
    Date date2=cal.getTime();
l=(date2.getTime()-date1.getTime())/(24*60*60*1000);
return l;
}
}

4.
import java.util.Scanner;

public class TestDayNum {
   
    private int startYear;
    private int startMonth;
    private int startDay;
   
    private int endYear;
    private int endMonth;
    private int endDay;
   

    private int outputStartYear;    //保存输入结果，供输出时使用
    private int outputStartMonth;
    private int outputStartDay;
   
    private int outputEndYear;
    private int outputEndMonth;
    private int outputEndDay;
   
    private int dayNum;
   
    private int tempYear;
    private int tempMonth;
    private int tempDay;
   
    Scanner scanner = new Scanner(System.in);
   
    public TestDayNum(){
        System.out.println("请输入起始日期: ");
        System.out.print("年: ");
        startYear = scanner.nextInt();
        outputStartYear = startYear;//输出时使用
       
        System.out.print("月: ");
        startMonth = scanner.nextInt();
        outputStartMonth = startMonth;
       
        System.out.print("日: ");
        startDay = scanner.nextInt();
        outputStartDay = startDay;
       
        System.out.println("请输入结束日期: ");
        System.out.print("年: ");
        endYear = scanner.nextInt();
        outputEndYear = endYear;
       
        System.out.print("月: ");
        endMonth = scanner.nextInt();
        outputEndMonth = endMonth;
       
        System.out.print("日: ");
        endDay = scanner.nextInt();   
        outputEndDay = endDay;
    }
   
    private void countDayNum() {
       
        if(this.startYear > this.endYear) {//起始年大于结束年，全部信息交换
            this.tempYear = this.endYear;
            this.endYear = this.startYear;
            this.startYear = this.tempYear;
           
            this.tempMonth = this.endMonth;
            this.endMonth = this.startMonth;
            this.startMonth = this.tempMonth;
           
            this.tempDay = this.endDay;
            this.endDay = this.startDay;
            this.startDay = this.tempDay;       
        }
      
        if(this.endYear == this.startYear){//若年相等
           
            if(this.endMonth < this.startMonth) {//起始月大于结束月，信息转换
                this.tempMonth = this.endMonth;
                this.endMonth = this.startMonth;
                this.startMonth = this.tempMonth;
               
                this.tempDay = this.endDay;
                this.endDay = this.startDay;
                this.startDay = this.tempDay;   
            }
           
            if(this.endMonth == this.startMonth){//若月相等
                this.dayNum = Math.abs(this.endDay - this.startDay);//结果
            }else {//年相等，月正确
                /*先算出两个月份中间的月份有多少天*/
                for(int i = this.startMonth + 1; i <= this.endMonth - 1; i++) {
                    this.dayNum += monthDayNum(i, this.startYear);
                }
               
                /*判断起始月的天数*/
                int startMonthDayNum = monthDayNum(this.startMonth, this.startYear);
                //加上起始月还剩下的天数
                this.dayNum += startMonthDayNum - this.startDay + 1;
                //加上结束月已经过了的天数
                this.dayNum += this.endDay - 1;
            }   
        }else {//年正确
            /*算出年之间的天数*/
            for(int i = this.startYear + 1; i <= this.endYear - 1;  i++) {
                if(isLeapyear(i)) {//如果是闰年
                    this.dayNum += 366;
                }else{
                    this.dayNum += 365;
                }
            }
           
            /*起始月距离该年结束的天数*/
            for(int i = this.startMonth + 1; i <= 12; i++) {
                this.dayNum += monthDayNum(i, this.startYear);
            }
           
            //判断起始月的天数
            int startMonthDayNum = monthDayNum(this.startMonth, this.startYear);
            //加上起始月还剩下的天数
            this.dayNum += startMonthDayNum - this.startDay + 1;
           
            /*结束月距离年初的天数*/
            for(int i = 1; i <= this.endMonth - 1; i++) {
                this.dayNum += monthDayNum(i, this.endYear);
            }
           
            //加上结束月已经过了的天数
            this.dayNum += this.endDay - 1;
        }
       
        System.out.println(this.outputStartYear + "年" + this.outputStartMonth + "月"
                           + this.outputStartDay + "日\n距离\n" + this.outputEndYear + "年"
                           + this.outputEndMonth + "月" + this.outputEndDay + "日\n有\n"
                           + this.dayNum + "天");
    }
   
    /**
     * 计算是否是闰年
     * @param year
     * @return
     */
    private boolean isLeapyear(int year)
    {
      if(year % 4 == 0 && year % 100 != 0 || year % 400 == 0){
        return true;
      }
      return false;
    }
   
    /**
     * 计算月份间的天数
     */
    private int monthDayNum(int tempMonth, int tempYear) {
        int dayNum = 0;
       
        switch (tempMonth){
        case 1:
        case 3:
        case 5:
        case 7:
        case 8:
        case 10:
        case 12: dayNum += 31;
                  break;
        case 4:
        case 6:
        case 9:
        case 11: dayNum += 30;
                  break;
        case 2: if(isLeapyear(tempYear)){
                     dayNum += 29;
                 }else{
                     dayNum += 28;
                 }
                 break;
        default: break;
        }
   
        return dayNum;
    }

    /**
     * @param args
     */
    public static void main(String[] args) {
        TestDayNum tdn = new TestDayNum();
        tdn.countDayNum();
    }
}