利用Java怎么对输入的日期进行判断

package com.ambow.www.ch03;
import java.util.Scanner;
public class Day {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		System.out.print("请输入年份");
		int year = sc.nextInt();
		System.out.print("请输入月份");
		int month = sc.nextInt();
		if(month<0 || month>12 || year<0) {
			System.out.println("请输入合法的年月！");
		}else {
			switch(month) {
				case 1:
				case 3:
				case 5:
				case 7:
				case 8:
				case 10:
				case 12:System.out.println("31天");break;
				case 4:
				case 6:
				case 9:
				case 11:System.out.println("30天");break;
					
			}
			if((year%100!=0&&year%4==0)||year%400==0) {
				if(month==2) {
					System.out.println("29天");
				}
			}else {
				if(month==2) {
					System.out.println("28天");
				}
			}
		}
	}
 
}