Question

请看如下java小程序，分别是用Switch分支结构和for循环实现的计算某一日期是当年第几天的程序。如何报错？

一、import java.util.Scanner;
public class CD{
public static void main(String[] args){
Scanner sc=new Scanner(System.in);
System.out.println("请依次输入年月日");
int year=sc.nextInt();
int month=sc.nextInt();
int day=sc.nextInt();
int num=0;
int a;
if((year%4==0&&year%100!=0)||year%400!=0){
a=1;
}else{
a=0;
}
int i;
for(i=1;i<month;i++){
if (i==2){
num=num+28+a;}
else if(((i<8)&&(i%2==1))||((i>7)&&(i%2==0))){
num=num+31;
}else{
num=num+30;
}
}num=num+day;
System.out.println("这天是第"+num+"天");
}
}
二、
import java.util.Scanner;
public class CountDate{
public static void main(String[] args){
Scanner sc=new Scanner(System.in);
System.out.println("请依次输入年月日");
int year=sc.nextInt();
int month=sc.nextInt();
int day=sc.nextInt();
int num=0;
switch(month){
case 12:
num=30+num;
case 11:
num=31+num;
case 10:
num=30+num;
case 9:
num=31+num;
case 8:
num=31+num;
case 7:
num=30+num;
case 6:
num=31+num;
case 5:
num=30+num;
case 4:
num=31+num;
case 3:
num=28+num;
case 2:
num=31+num;
case 1:
num=day+num;
break;
default :
System.out.println("Eorror!");
break;
}
if((year%4==0&&year%100!=0)||year%400!=0)
{
num=num+1;}
System.out.println("这天是第"+num+"天");
}
}

import java.util.Scanner;
public class CountDate{
public static void main(String[] args){
Scanner sc=new Scanner(System.in);
System.out.println("请依次输入年月日");
int year=sc.nextInt();
int month=sc.nextInt();
int day=sc.nextInt();
int num=0;
switch(month){
case 12:
num=30+num;
case 11:
num=31+num;
case 10:
num=30+num;
case 9:
num=31+num;
case 8:
num=31+num;
case 7:
num=30+num;
case 6:
num=31+num;
case 5:
num=30+num;
case 4:
num=31+num;
case 3:
num=28+num;
case 2:
num=31+num;
case 1:
num=day+num;
break;
default :
System.out.println("Eorror!");
break;
}
if((year%4==0&&year%100!=0)||year%400!=0)
{
num=num+1;}
System.out.println("这天是第"+num+"天");
}
}

请问这两个程序如何添加报错的语句？就是说，如果输入4月31 12月32，非闰年输入2月29号 等错误日期，要使程序能够识别，应当怎么添加代码是最简单最方便的？？

Answer 1

自己建个判断语句或者用Date类。

把程序写的那么复杂，一个数组就能把你的一堆分支和循环替换掉。

追问

因为数组还没学习到。 刚刚学了三四天。

追答

import java.util.Scanner;
class MyDate
{
public static void main(String args[])
{
Scanner sc=new Scanner(System.in);
System.out.println("请依次输入年月日");
int year = sc.nextInt();
int month = sc.nextInt();
int day = sc.nextInt();

int num = day;
int[] date = null;
if((year % 4 == 0 && year % 100 != 0) || year % 400 == 0)
{
date = new int[]{31, 29, 31, 30, 31, 30, 31, 31, 30, 31, 30};
}
else
{
date = new int[]{31, 28, 31, 30, 31, 30, 31, 31, 30, 31, 30};
}

if(day > date[month - 1] || day <= 0)
{
System.out.println(("日期有误！"));
}
else
{
for(int i = 0; i < month - 1; i++)
{
num += date[i];
}
System.out.println(("这天是第" + num + "天"));
}
}
}

Answer 2

用if 如果是输出语句

Answer 3

if(....) throw new Exception();