ROT13 Program Easy Method

ROT 13 Program in JAVA

ROT 13 means ROTATE 13. It is an Encryption Scheme which works by cyclic shifting of each Lower Case and Upper Case letter 13 position.

Example :- 

Input - Encryption

Output - Rapelcgvba

Input : Mind 

Output : Zvaq

Algorithm and Program given below :-

Algorithm :-

Logic - Divide total alphabets into 2 halves i.e. first half is A-M and Second half is N-Z. ( Same for lower case also).

Step 1 - Input a word in a variable and find its length.

Step 2 - Extract each character and check whether it is in A-M range or N-Z range.

Step 3 - If the character is in the first half then increment the value of ASCII code by 13 by using type casting. If the character is in the second half then decrease the value of ASCII code by 13 by using type casting.

Step 4 - convert the new ASCII code into character in a new variable.

Step 5 - Store the new character in new string variable. (Say this word is Encrypted word)

Step 6 - Display both Original and Encrypted word.

Program :- 

import java.io.*;
import java.util.*;
class ROT13
{
    public static void main(String args[])
    {
        Scanner in= new Scanner(System.in);
        String str,str1= ""; // string variables to store words
        char ch,ch1; // character variables
        int i,y,l; // 'i' for loop , 'y' to convert letter into integer
        System.out.println("Enter Message");
        str= in.nextLine(); // storing original word
        l= str.length(); // storing length of the word
        for(i=0;i<l;i++)
        {
            ch= str.charAt(i); // extracting character of the string
            if(ch>='A'&&ch<='M'||ch>='a'&&ch<='m')
            {
                y=(int)ch+13;
                ch=(char)y;
                str1=str1+ch;
            }
            else if(ch>='N'&&ch<='Z'||ch>='n'&&ch<='z')
            {
                y=(int)ch-13;
                ch=(char)y;
                str1=str1+ch;
            }
        }
        System.out.println("Original Message : " +str); // Printing Original String
        System.out.println("Encrypted Message : " +str1); // Printing Encrypted String
    } // End of Main
} // End of Class

All the Best :)
Keep Learning :)

Another way : ROT13 Program alternate method