Answer:
Here is the JAVA program that produces Caeser cipher o given message string:
import java.util.Scanner; //to accept input from user
public class Main {
public static void main(String args[]) { //start of main function
Scanner input = new Scanner(System.in); //creates object of Scanner
System.out.println("Enter the message : "); //prompts user to enter a plaintext (message)
String message = input.nextLine(); //reads the input message
System.out.println("Enter the amount by which by which to rotate each letter : "); //prompts user to enter value of shift to rotate each character according to shift
int rotate = input.nextInt(); // reads the amount to rotate from user
String encoded_m = ""; // to store the cipher text
char letter; // to store the character
for(int i=0; i < message.length();i++) { // iterates through the message string until the length of the message string is reached
letter = message.charAt(i); // method charAt() returns the character at index i in a message and stores it to letter variable
if(letter >= 'a' && letter <= 'z') { //if letter is between small a and z
letter = (char) (letter + rotate); //shift/rotate the letter
if(letter > 'z') { //if letter is greater than lower case z
letter = (char) (letter+'a'-'z'-1); } // re-rotate to starting position
encoded_m = encoded_m + letter;} //compute the cipher text by adding the letter to the the encoded message
else if(letter >= 'A' && letter <= 'Z') { //if letter is between capital A and Z
letter = (char) (letter + rotate); //shift letter
if(letter > 'Z') { //if letter is greater than upper case Z
letter = (char) (letter+'A'-'Z'-1);} // re-rotate to starting position
encoded_m = encoded_m + letter;} //computes encoded message
else {
encoded_m = encoded_m + letter; } } //computes encoded message
System.out.println("Encoded message : " + encoded_m.toUpperCase()); }} //displays the cipher text (encoded message) in upper case letters
Explanation:
The program prompts the user to enter a message. This is a plaintext. Next the program prompts the user to enter an amount by which to rotate each letter. This is basically the value of shift. Next the program has a for loop that iterates through each character of the message string. At each iteration it uses charAt() which returns the character of message string at i-th index. This character is checked by if condition which checks if the character/letter is an upper or lowercase letter. Next the statement letter = (char) (letter + rotate); is used to shift the letter up to the value of rotate and store it in letter variable. This letter is then added to the variable encoded_m. At each iteration the same procedure is repeated. After the loop breaks, the statement System.out.println("Encoded message : " + encoded_m.toUpperCase()); displays the entire cipher text stored in encoded_m in uppercase letters on the output screen.
The logic of the program is explained here with an example in the attached document.
In this exercise we have to use the computer language knowledge in JAVA to write the code as:
the code is in the attached image.
In a more easy way we have that the code will be:
import java.util.Scanner;
public class Main {
public static void main(String args[]) {
Scanner input = new Scanner(System.in);
System.out.println("Enter the message : ");
String message = input.nextLine();
System.out.println("Enter the amount by which by which to rotate each letter : ");
int rotate = input.nextInt();
String encoded_m = "";
char letter;
for(int i=0; i < message.length();i++) {
letter = message.charAt(i);
if(letter >= 'a' && letter <= 'z') {
letter = (char) (letter + rotate);
if(letter > 'z') {
letter = (char) (letter+'a'-'z'-1); }
encoded_m = encoded_m + letter;}
else if(letter >= 'A' && letter <= 'Z') {
letter = (char) (letter + rotate);
if(letter > 'Z') {
letter = (char) (letter+'A'-'Z'-1);}
encoded_m = encoded_m + letter;}
else {
encoded_m = encoded_m + letter; } }
System.out.println("Encoded message : " + encoded_m.toUpperCase()); }}
See more about JAVA at brainly.com/question/2266606
