Decoding Encoded Message

 /*The Computer Department of the Agency of International Espionage is trying to decode intercepted messages. The agency’s spies have determined that the enemy encodes messages by first converting all characters to their ASCII values and then reversing the string.
For example consider A_z ( the underscore is just to highlight the space. The ASCII values of A, <space>, z are 65, 32 and 122 respectively. Concatenate them to get 6532122, then reverse this to get 2212356 as the coded message.
Write a program which reads a coded message and decodes it. The coded message will not exceed 200 characters. It will contain only alphabets (A..Z and a..z) and spaces. ASCII values of A…Z are 65 to 90 and those of a..z are 97 to 122.
Sample Output
Enter the encoded message
2312179862310199501872379231018117927

The decoded message is ::  Have A Nice Day*/

import java.io.*;
class Q2_2004
{
    //Data Members
    public String msg;
    public String ans;
    public String rev;
    public int len;
    public String newans;
      
    //Methods
    //Default Constructor
    Q2_2004()
    {
        msg="";
        ans="";
        rev="";
        len=0;
        newans="";
    }
  
    //Function to input the encoded message
    public void Input()
    throws IOException
    {
        BufferedReader br=new BufferedReader(new InputStreamReader(System.in));
      
        int i,len1;
        System.out.println("Enter the encoded message");
        msg=br.readLine();
        len1=msg.length();
        for(i=(len1-1);i>=0;i--)
           rev+=msg.charAt(i);
        len=rev.length();
    }
  
    //Function to extract the digits from the reverse number and decode it
    public void Decode()
    throws IOException
    {
        Input();
        int lwrnum[]={97,98,99,100,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122};
        char lwrcas[]={'a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z'};
        int uprnum[]={65,66,67,68,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90};
        char uprcas[]={'A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z'};
      
        int i,j;
        int digit;
        int number=0;
        for(i=0;i<len;i++)
        {
            digit=Integer.parseInt(rev.substring(i,i+1));
            number=number*10+digit;
          
            if(number>=65 && number <=90)
            {
               for(j=0;j<26;j++)
               {
                   if(number==uprnum[j])
                     ans+=uprcas[j];
                }//j
                number=0;
            }//if
            else
            if(number>=97 && number <=122)
            {
               for(j=0;j<26;j++)
               {
                   if(number==lwrnum[j])
                     ans+=lwrcas[j];
                }//j
                number=0;
            }//if
            else
            if(number==32)
            {
              ans+=" ";
              number=0;
            }
         }//i
         ans=" "+ans;
         ans+=" ";
         len=ans.length();
       
         char ltr;
         for(i=0;i<len;i++)
         {
             ltr=ans.charAt(i);
             if(ltr!=' ')
               newans+=ltr;
             else
             if(ltr==' ')
             {
                 newans+=ltr;
                 ltr=ans.charAt(i+1);
                 for(j=0;j<26;j++)
                 {
                     if(ltr==lwrcas[j])
                        ltr=uprcas[j];
                 }
                 newans+=ltr;
                 i++;
             }//if
         }
    }
  
    //Function to Display the string
    public void Display()
    throws IOException
    {
        Decode();
        System.out.print("The decoded message is :: "+newans);
    }
}
                      
class Q2_2004main
{
    public void main()
    throws IOException
    {
        Q2_2004 SM=new Q2_2004();
        SM.Display();
    }
}