求两个时间段相差的天数，具体到某月某号

package com.util.demo;

public class DiffYear {

/**
* @param args
*/
public static void main(String[] args) {
int year1 = 2000;
int year2 = 2015;
System.out.println(year1 + "与" + year2 + "相差的天数："
+ getDiffDay(year1, year2));
String y1="19830117",y2="20140219";
System.out.println(y1 + "与" + y2 + "相差的天数："
+ getDiffDay(y1, y2));
}

/*
* 取得两个年份相差的天数
*/
public static long getDiffDay(int y1, int y2) {
long sum = 0;
for (int year = y1; year < y2; year++) {
if (year % 4 == 0 && year % 100 != 0 || year % 400 == 0) {
sum += 366;
} else {
sum += 365;
}
}
return sum;
}

/**
* 求两个年份之间相差的天数，具体到某个月份 比如1900年4月1号到2015年5月7号相差的天数
*
* @param y1
* @param y2
* @return
*/
public static long getDiffDay(String y1, String y2) {
long sum = 0;
String yearStr1 = y1.substring(0, 4);
String monthStr1 = y1.substring(4, 6);
String dayStr1 = y1.substring(6,;
int year1 = getVal(yearStr1);
int mont1 = getVal(monthStr1);
int day1 = getVal(dayStr1);
String yearStr2 = y2.substring(0, 4);
String monthStr2 = y2.substring(4, 6);
String dayStr2 = y2.substring(6,;
int year2 = getVal(yearStr2);
int mont2 = getVal(monthStr2);
int day2 = getVal(dayStr2);
int sjyear1 = year1 + 1;// 实际计算的时候，计算开始年份的下一年
int sjyear2 = year2 - 1;// 实际计算的时候，计算结束年份的上一年
for (int i = sjyear1; i < sjyear2; i++) {
// 判断是否为闰年
if (i % 4 == 0 && i % 100 != 0 || i % 400 == 0) {
sum += 366;
} else {
sum += 365;
}
}
// 判断开始的年对应月份
for (int i = 1; i < mont1; i++) {
if (mont1 == 2) {
if (year1 % 4 == 0 && year1 % 100 != 0 || year1 % 400 == 0) {
sum += 29;
} else {
sum += 28;
}
} else {
if (mont1 == 4 || mont1 == 6 || mont1 == 9 || mont1 == 11) {
sum += 30;
} else {
sum += 31;
}
}
}
// 判断结束的年对应月份
for (int i = 1; i < mont2; i++) {
if (mont2 == 2) {
if (year2 % 4 == 0 && year2 % 100 != 0 || year2 % 400 == 0) {
sum += 29;
} else {
sum += 28;
}
} else {
if (mont2 == 4 || mont2 == 6 || mont2 == 9 || mont2 == 11) {
sum += 30;
} else {
sum += 31;
}
}
}
sum = sum + day1 + day2;
return sum;
}

public static int getVal(String str) {
int num = 0;
if (str.startsWith("0")) {
str = str.substring(1, str.length());
}
num = Integer.parseInt(str);
return num;
}

}