根据年份(已考虑平闰年)和月份计算天数：switch...case..

package day1;

public class Days {
	public static void main(String[] args) {
		//根据年份和月份计算天数
		int year = 2001; //年
		int month = 9;   //月
		int days = 0;    //天数
		switch(month){
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
		case 12:
			days = 31;
			break;
		case 4:
		case 6:
		case 9:
		case 11:
			days = 30;
			break;
		case 2:
			if(year%4==0 && year%100!=0 || year%400==0){
				days = 29;
			}else{
				days = 28;
			}
		}
		System.out.println("days="+days);
    }
}