Java code. I have this programming problem that already has been solved: Create
ID: 3914065 • Letter: J
Question
Java code.
I have this programming problem that already has been solved:
Create an interface MessageEncoder that has a single abstract method encode(plainText), where plainText is the message to be encoded. The method will return the encoded message.
Create a class SubstitutionCipher that implements the interface MessageEncoder, as described above. The constructor should have one parameter called shift. Define the method encode so that each letter is shifted by the value in shift. Defne the method encode so that each letter is shifted by the value in shift. For example, if shift is 3, a will be replaced by d, b will be replaced by e, c will be replaced by f, and so on. (Hint: You may wish to define a private method that shifts a single character.)
Create a class ShuffleCipher that implements the interface MessageEncoder, as described above. The constructor should have one parameter called n. Define the method encode so that the message is shuffled n times. To perform one shuffle, split the message in half and then take characters from each half alternately. For example, if the message is abcdefghi, the halves are abcde and fghi. The shuffled message is afbgchdie. (Hint: You may wish to define a private method that performs one shuffle.
What I actually need is to modify the given code from already solved programming problem 2
the code is given in this link https://www.chegg.com/homework-help/questions-and-answers/messageencoder-java-create-interface-messageencoder-single-abstract-method-encode-plaintex-q5674325
I need the following modifications:
Create an interface MessageDecoder that has a single abstract method decode(cipherText), where cipherText is the message to be decoded. The method will return the decoded message. Modify the classes SubstitutionCipher and ShuffleCipher, as described in Programming Problem 2, above, so that they implement MessageDecoder as well as the interface MessageEncoder described above. Finally, write a program that allows a user to encode and decode messages entered on the keyboard.
Explanation / Answer
interface MessageEncoder{
public String encode(String plainText);
public String decode(String ciperText);
}
class SubstitutionCipher implements MessageEncoder{
int offset;
SubstitutionCipher(int shift){
offset=shift;
}
public String encode(String plainText) {
// declare constants
final int ALPHABET_SIZE = 26; // used to wrap around A-Z
String encoded = ""; // base for string to return
char letter; // letter being processed
// convert message to upper case
plainText = plainText.toUpperCase();
// process each character of the message
for (int index = 0; index < plainText.length(); index++)
{
// get the letter and determine whether or not to
// add the cipher value
letter = plainText.charAt(index);
if (letter >='A' && letter <= 'Z')
{
// is A-Z, so add offset
// determine whether result will be out of A-Z range
if ((letter + offset) > 'Z') // need to wrap around to 'A'
letter = (char)(letter - ALPHABET_SIZE + offset);
else
if ((letter + offset) < 'A') // need to wrap around to 'Z'
letter = (char)(letter + ALPHABET_SIZE + offset);
else
letter = (char) (letter + offset);
}
// build encoded message string
encoded = encoded + letter;
}
return encoded;
}
public String decode(String ciperText) {
// declare constants
final int ALPHABET_SIZE = 26; // used to wrap around A-Z
String decoded = ""; // base for string to return
char letter; // letter being processed
// make ciperText message upper case
ciperText = ciperText.toUpperCase();
// process each letter of message
for (int index = 0; index < ciperText.length(); index++)
{
// get letter and determine whether to subtract cipher value
letter = ciperText.charAt(index);
if (letter >= 'A' && letter <= 'Z')
{
// is A-Z, so subtract cipher value
// determine whether result will be out of A-Z range
if ((letter - offset) < 'A') // wrap around to 'Z'
letter = (char)(letter + ALPHABET_SIZE - offset);
else
if ((letter - offset) > 'Z') // wrap around to 'A'
letter = (char)(letter - ALPHABET_SIZE - offset);
else
letter = (char) (letter - offset);
}
// build decoded message
decoded = decoded + letter;
}
return decoded;
}
}
class ShuffleCipher implements MessageEncoder{
private int n;
public ShuffleCipher(int n){
this.n = n;
}
public String encode(String plainText){
String cipherText = plainText;
for(int i=0; i<n; i++){
cipherText = shuffle(cipherText);
}
return cipherText;
}
private String shuffle(String s){
String shuffled = "";
int mid = s.length()/2;
String first = s.substring(0, mid);
String second = s.substring(mid, s.length());
for(int i=0;i<first.length(); i++){
shuffled = shuffled + first.charAt(i) + second.charAt(i);
}
// if the length of the message is odd; add in the last character
if(second.length() > first.length()){
shuffled = shuffled + second.charAt(second.length()-1);
}
return shuffled;
}
public String decode(String cipherText){
String plainText = cipherText;
for(int i=0; i<n;i++){
plainText = unshuffle(plainText);
}
return plainText;
}
private String unshuffle(String s){
String unshuffled = "";
for(int i=0;i<s.length();i+=2){
unshuffled = unshuffled + s.charAt(i);
}
for(int i=1;i<s.length();i+=2){
unshuffled = unshuffled + s.charAt(i);
}
return unshuffled;
}
}
public class Main{
public static void main(String args[]){
SubstitutionCipher obj=new SubstitutionCipher(3);
System.out.println(obj.encode("hai"));
System.out.println(obj.decode("KDL"));
ShuffleCipher obj2=new ShuffleCipher(1);
System.out.println(obj2.encode("abcdefghi"));
}
}
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