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、32

import javax.swing.JOptionPane; 

public class TestNumber 

{   

    public static void main(String args[]) 

    { 

        loopNumber();    

    } 

     static  void loopNumber(){ 

        int number=0,d5,d4,d3,d2,d1; 

        String str=JOptionPane.showInputDialog("输入一个1至99999之间的数"); 

        number=Integer.parseInt(str); 

        if(number>=1&&number<100000) //判断number在1至99999之间的条件  

            { 

               d5=number/10000 ;  //计算number的最高位（万位）d5  

               d4=(number-d5*10000)/1000;   //计算number的千位d4  

               d3=number%1000/100;   //计算number的百位d3  

                d2=number%100/10; 

                d1=number%10; 

              if(d5!=0)  //判断number是5位数的条件  

                { 

                  System.out.println(number+"是5位数"); 

                  if(d5==d1&&d4==d2) //判断number是回文数的条件  

                   { 

                      System.out.println(number+"是回文数"); 

                   } 

                  else 

                   {  

                     System.out.println(number+"不是回文数"); 

                   } 

                } 

              else if(d4!=0)  //判断number是4位数的条件  

                { 

                   System.out.println(number+"是4位数"); 

                   if(d4==d1&&d3==d2) //判断number是回文数的条件码  

                   { 

                        System.out.println(number+"是回文数"); 

                   } 

                  else 

                   {  

                      System.out.println(number+"不是回文数"); 

                   } 

                } 

                else if(d3!=0)  //判断number是3位数的条件  

                { 

                   System.out.println(number+"是3位数"); 

                   if(d3==d1) //判断number是回文数的条件  

                   { 

                        System.out.println(number+"是回文数"); 

                   } 

                  else 

                   {  

                    System.out.println(number+"不是回文数"); 

                   } 

                } 

             else if(d2!=0) 

                { 

                  System.out.println(number+"是2位数"); 

                   if(d1==d2) 

                   { 

                       System.out.println(number+"是回文数"); 

                   } 

                  else 

                   {  

                     System.out.println(number+"不是回文数"); 

                   } 

                } 

             else if(d1!=0) 

                { 

                  System.out.println(number+"是1位数"); 

                   System.out.println(number+"是回文数"); 

                } 

            } 

         else 

            { 

               System.out.printf("\n%d不在1至99999之间",number); 

            } 

    } 

}