实验二 （二） 判断回文数

（2）编写一个Java应用程序。用户从键盘输入一个1—9999之间的数，程序将判断这个数是几位数，并判断这个数是否是回文数。回文数是指将该数含有的数字逆序排列后得到的数和原数相同，例如12121、3223都是回文数。

如何从键盘输入一个数呢？

package test;
import java.util.Scanner;
public class KeyboardInput {
    public static void main(String[] args){
        Scanner x = new Scanner(System.in);//构造一个Scanner对象，其传入参数为System.in 
        System.out.println("请输入一个整数");
        int i = x.nextInt();//读取一个int数值
        System.out.println("你输入的数字是："+i);
    }
}

package hi;
import java.util.Scanner;
public class Palindrome {
    public static void main(String[] args){
        Scanner x = new Scanner(System.in);//构造一个Scanner对象，其传入参数为System.in 
        System.out.println("请输入一个整数");
        int num= x.nextInt();//读取一个int数值
        int a1,a2,a3,a4,a5;
        a5=num/10000;
        a4=num%10000/1000;
        a3=num%1000/100;
        a2=num%100/10;
        a1=num%10;
        if(a5!=0){
            System.out.println(num+" is 5 digits");
            if(a5==a1&&a2==a4){
                System.out.println(num+" is a palindrome");
            }else{
                System.out.println(num+" is not a palindrome");
            }
        }
        else if(a4!=0){
            System.out.println(num+" is 4 digits");
            if(a1==a4&&a2==a3){
                System.out.println(num+" is a palindrome");
            }else{
                System.out.println(num+" is not a palindrome");
            }
        }
        else if(a3!=0){
            System.out.println(num+" is 3 digits");
            if(a1==a3){
                System.out.println(num+" is a palindrome");
            }else{
                System.out.println(num+" is not a palindrome");
            }
            
        }
        else if(a2!=0){
            System.out.println(num+" is 2 digits");
            if(a1==a2){
                System.out.println(num+" is a palindrom");
                
            }
            else{
                System.out.println(num+" is not a palindrom");
            }
                
        }
        else if(a1!=0){
            System.out.println(num+" is 1 digits");
            System.out.println(num+" is a palindrom");
        }
        else{
            System.out.println(num+" is not between 0 and 99999");
        }
             
    }
}