Question

Write a cencrypt() function that takes a arbitrary length string and an integer as inputs and returns a string as output.

The cencrypt() function you write in lab today needs to work on strings that contain upper-case letters, lower-case letters, or both. The output string should be all upper-case letters. (The Romans of Caesar's time used only what today we call upper-case letters.)

So a call to cencrypt("Caesar", 1) should return (return not print) the string “DBFTBS” and a call to cencrypt(“DBFTBS”, -1)should return the string "CAESAR".

The string function .upper() mentioned in the assigned reading in Chapter 7.3 of Zybooks that gives back a version of its string that has all alphabet characters converted to upper case may be useful here.

Answer 1

CODE IN JAVA:

Cencrypt.java file:

import java.util.Arrays;

public class Cencrypt {
   public static String cencrypt(String input,int n) {
       input = input.toUpperCase();
       int len = input.length();
       int temp;
       char arr[]=new char[len];
       for(int i=0;i<len;i++) {
           temp = charToInt(input.charAt(i))+n;
           if(temp>26)
               temp = temp - 26;
           else if(temp<1)
               temp = temp + 26;
           arr[i] = intToChar(temp);
       }
       return Arrays.toString(arr)
       .substring(1, 3*arr.length-1)
       .replaceAll(", ", "");
   }
   //method to get corresponding character
   static char intToChar(int n) {
       char alpha[] = {'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'};
       return alpha[n-1];
   }
   //method to get corresponding integer
   static int charToInt(char ch) {
       char alpha[] = {'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'};
       for(int i=0;i<alpha.length;i++) {
           if(alpha[i]==ch) {
               return i+1;
           }
       }
       return 0;
   }
   public static void main(String[] args) {
       String input = "Caesar";
       System.out.println("The input string is:"+input);
       //calling the methods and displaying the result
       String output = cencrypt(input,1);
       System.out.println("After calling the cencrypt method with n=1 the output is:"+output);
       String temp = cencrypt(output,-1);
       System.out.println("After calling the cencrypt method with n=-1 the output is:"+temp);
   }

}
OUTPUT: