Java函数2:计算两个日期相差的天数

import java.util.Scanner;
public class HelloWorld {
public static void main(String[] args){
//	Scanner s = new Scanner(System.in);
//	System.out.println("请输入一个数字");
//	int num = s.nextInt();
int SUM = Caluater_date_sub_day(2009,1,25,2008,1,10);
System.out.println(SUM);
}
//判断闰年平年
public static boolean isLeap(int y){
if((y % 4 == 0 && y % 100 != 0) || y % 400 == 0)
return true ;
return false ;
}
//判断一年已经过了多少天
public static int GetDay(int y , int m , int d){
int sum = 0 ;
switch(m){
case 12 : sum += 31 ;
case 11 : sum += 30 ;
case 10 : sum += 31 ;
case 9  : sum += 30 ;
case 8  : sum += 31 ;
case 7  : sum += 31 ;
case 6  : sum += 30 ;
case 5  : sum += 31 ;
case 4  : sum += 30 ;
case 3  : sum += 31 ;
case 2  :
if(isLeap(y) == true)
sum += 29 ;
else
sum += 28 ;
case 1  : sum += 31 ;
sum += d ;
}
return d ;
}
//判断一年还剩下多少天
public static int OthearDay(int y , int m , int d)
{
if(isLeap(y) == true)
return 366 - GetDay(y , m , d);
return 365 - GetDay(y, m, d) ;
}
//判断两个日期相差的天数
public static int Caluater_date_sub_day(int y1,int m1,int d1,int y2,int m2 ,int d2)
{
if(y1 == y2){
int day1 = GetDay(y1, m1, d1) - GetDay(y2, m2, d2) ;
return abs(day1);
}
else if(y1 < y2){
int sum1 = OthearDay(y1, m1, d1) ;
int sum2 = GetDay(y2, m2, d2) ;
int sum3 = 0 ;
for(int i = y1 + 1 ; i < y2 ; i++){
if(isLeap(i))
sum3+=366 ;
else
sum3+=365 ;
}
return sum1+sum2+sum3 ;
}else
{
int sum1 = GetDay(y1, m1, d1) ;
int sum2 = OthearDay(y2, m2, d2) ;
int sum3 = 0 ;
for(int i = y2 + 1 ; i < y1 ; i++){
if(isLeap(i))
sum3+=366 ;
else
sum3+=365 ;
}
return sum1+sum2+sum3 ;
}
}
//计算一个数的绝对值
public static int abs(int num){
return num > 0 ? num : -num ;
}
}