JAVA PROGRAMMING : ALSO NEED TESTER CODES - Alice recently read the news about E

Question

JAVA PROGRAMMING : ALSO NEED TESTER CODES - Alice recently read the news about Edward Snowden, and learned that encryption could be used to
protect personal communication effectively. She decided to construct a simple encryption scheme to
protect her own communications as follows. First, she generates a set of randomly chosen "secret keys"
K1, K2, K3. Next, using these keys, she encrypts a set of messages M1, M2, M3, obtaining ciphertexts
C1= K1 + M1, C2= K2+ M2, C3 =K3+M3.
In implementing her scheme, she decides to choose the secret keys from the set A={1, 2, ..., 100}, and
the messages from the sequence B=(a, b, c, ..., z). She is adamant that her ciphertexts should also be
elements of the sequence B; to this end, she defines the "+" operator in expressions such as C1=K1+M1
to shift element M1 in B to the right by K1 positions. For example, if K1=1 and M1= b, then the
corresponding ciphertext is C1= c. Similarly, if K1=2 and M1=b, then the ciphertext is C1=d, if K1=24 and
M1=b, the ciphertext is C1=z, and if K1=25 and M1=b, then the ciphertext is C1=a.

Requirements:
1. the file name must named as Problem2.java
2. a static method:
public static String encryptMessage(int[] secretKeys, String message)

Input
The input consists of four rows.
a. The first row is an integer n satisfying 1 <= n <= 100 specifying the number of secret keys.
b. The second row is a sequence of n integers, each from the set A={1,2,..,100}, corresponding to the secret keys.
c. The third row is a sequence of symbols from the set B={a,b,..,z} corresponding to the messaged to be encrypted.
d. The fourth row is a special value -1 to indicate the end of the input phase.

Output
Output a single row of symbols from set B corresponding to each of the ciphertexts.

Sample Input
3
1 2 3
bzy
-1

Sample Output
cbb

Explanation / Answer

Problem2.java

public class Problem2 {

   public static String encryptMessage(int[] secretKeys, String message){
      
       int msgLen = message.length();
       String encrptText = "";
       for(int i = 0;i<msgLen;i++){
           int charValue = message.charAt(i)+secretKeys[i];
           while(charValue<97 || charValue>122){
               charValue -= 26;
           }
           encrptText += (char) charValue;
       }
       return encrptText;
   }
}

TestClass.java

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class TestClass {
   public static void main(String[] args) {

       BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
       int n;
       int[] secretKeys = null;
       String plainText= null;;
      
       try {
           System.out.print("Enter the value of n");
           n = Integer.parseInt(br.readLine());
          
           secretKeys = new int[n];
           System.out.println("Enter the secret keys:");
           String[] strKeys = br.readLine().split(" ");
           for(int i = 0; i<n;i++){
               secretKeys[i] = Integer.parseInt(strKeys[i]);
           }
          
           System.out.print("Enter the message:");
           plainText = br.readLine();
          
           System.out.print("Enter end of input delimeter:");
           while(true){
               String delimeter = br.readLine();
               if(Integer.parseInt(delimeter) == -1){
                   break;
               }
               System.out.println("Please enter the valid end of input delimeter");
              
           }
          
       } catch (NumberFormatException e) {
           System.out.println("Invalid Value");
           e.printStackTrace();
       } catch (IOException e) {
           System.out.println("Pleaes enter correct values");
           e.printStackTrace();
       }
      
       System.out.println("Encrypted Output:");
       System.out.println(Problem2.encryptMessage(secretKeys, plainText));
      
   }

}

Note: We can remove system.out statement while taking input if we don't want

Test results:

Enter the value of n:5
Enter the secret keys:
1 2 3 1 52
Enter the message:abczb
Enter end of input delimeter:-1
Encrypted Output:
bdfab

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