问题，输入某年某月某日，判断这一天是这一年的第几天？(这是我用java写的代码如下：）

请教各位大侠，改怎么改，菜鸟才刚刚开始学java。非常感谢！
public static void main(String[] args) {
// TODO Auto-generated method stub
int year，lemp;
int month=3，day=12;
int i;
switch(month){
case 1:i=0;break;
case 2:i=30;break;
case 3:i=58;break;
case 4:i=89;break;
case 5:i=119;break;
case 6:i=150;break;
case 7:i=180;break;
case 8:i=211;break;
case 9:i=242;break;
case 10:i=273;break;
case 11:i=303;break;
case 12:i=334;break;
//default;
}
i=i+day;
if(year%400==0||(year%100!=0&&year%4==0)){ //判断是否为闰年
lemp=1;
}else
lemp=0;

if(lemp==1&&month>2){ // 如果是闰年且月份大于二，总天数应该加一
i++;
}
System.out.println("这一天是以年中的第："+i+"天！");
}
}

public static void main(String[] args) {
// TODO Auto-generated method stub
int year = 2012, lemp;
int month = 2, day = 21;
int i = 0;
switch (month) {
case 1:
i = 0;
break;
case 2:
i = 31;
break;
case 3:
i = 59;
break;
case 4:
i = 90;
break;
case 5:
i = 120;
break;
case 6:
i = 151;
break;
case 7:
i = 181;
break;
case 8:
i = 212;
break;
case 9:
i = 243;
break;
case 10:
i = 273;
break;
case 11:
i = 304;
break;
case 12:
i = 334;
break;
// default;
}
i = i + day;
if (year % 400 == 0 || (year % 100 != 0 && year % 4 == 0)) { // 判断是否为闰年
lemp = 1;
} else
lemp = 0;

if (lemp == 1 && month > 2) { // 如果是闰年且月份大于二，总天数应该加一
i++;
}
System.out.println("这一天是以年中的第：" + i + "天！");
}

注意一月是31天哦！！！
按照你的思路可以这样改，但是还有别的更好办法

完整修改如下： public static void main(String[] args) { int year = 2011, lemp; int month = 3, day = 11; int i = 0; switch (month) { case 1: i = 0; break; case 2: i = 30; break; case 3: i = 58; break; case 4: i = 89; break; case 5: i = 119; break; case 6: i = 150; break; case 7: i = 180; break; case 8: i = 211; break; case 9: i = 242; break; case 10: i = 273; break; case 11: i = 303; break; case 12: i = 334; break; // default; } i = i + day; if (year % 400 == 0 || (year % 100 != 0 && year % 4 == 0)) {//判断是否为闰年 lemp = 1; } else lemp = 0; if (lemp == 1 && month > 2) {// 如果是闰年且月份大于二，总天数应该加一 i++; } System.out.println("这一天是以年中的第："+i+"天！"); }

import java.text.simpledateformat; import java.util.calendar; import java.util.scanner; public class getdate { public static void main(string[] args) { scanner scanner = new scanner(system.in); system.out.println("请输入年:"); int year = scanner.nextint(); system.out.println("请输入月:"); int month = scanner.nextint(); system.out.println("请输入日:"); int day = scanner.nextint(); calendar calendar1 = calendar.getinstance(); calendar1.set(year, 0, 1); long time1 = calendar1.gettimeinmillis(); calendar calendar2 = calendar.getinstance(); calendar2.set(year, month - 1, day); long time2 = calendar2.gettimeinmillis(); long result = (time2 - time1) / 1000 / 60 / 60 / 24; simpledateformat format = new simpledateformat("yyyy/mm/dd"); system.out.println(format.format(calendar2.gettime()) + "距离" + format.format(calendar1.gettime()) + "有" + result + "天"); } }