Question

Programming Message Encoder - Write in Java and include comments

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.)

Grading Rubric

Task	Points
Working solution for the problem	6
Best practices in programming	2
Total	8

Answer 1

for shift

code in java

import java.io.*;

import java.util.Scanner;//import scanner class for taking input from uer

interface MessageEncoder//creates interface named MessageEncoder

{

String encode( String plainText);//declare the encode method with return type string and argument string

}

class SubstitutionCipher implements MessageEncoder//class that implements the interface MessageEncoder

{

int shift;//integer shift

SubstitutionCipher(int shift)//constuctor that have one parameter

{

this.shift=shift;

}

private char ShiftSingleCharacter(char s)//private method that shift one character

{

return ((char)(((s - 'a' + this.shift) % 26) + 'a'));//return the shifted character

}

public String encode(String plainText)//abstract method implementation

{

String ans="";//ans string that holds the shifted characters

for (char c : plainText.toCharArray()) //first assgin the plainText characters to char c array

{

ans+=Character.toString((ShiftSingleCharacter(c)));//and call ShiftSingleCharacter for every single character in the plaintext

}

return ans;//return the ans

}

public static void main (String[] args)

{

Scanner input = new Scanner(System.in);//creates the object of the scanner class

System.out.print("Enter message : ");

String PlainText=input.nextLine();//taking plain text from the user

System.out.print("Enter Shift : ");//taking shift from the user

int shift=input.nextInt();

SubstitutionCipher t=new SubstitutionCipher(shift);//creates the object of the class SubstitutionCipher

String s=t.encode(PlainText);//calling the method encode

System.out.println("Shifted message is :"+s);//prints the ans

}

}

output

For shuffle

code in java

import java.io.*;

import java.util.Scanner;//import scanner class for taking input from uer

interface MessageEncoder//creates interface named MessageEncoder

{

String encode( String plainText);//declare the encode method with return type string and argument string

}

class ShuffleCipher implements MessageEncoder//class that implements the interface MessageEncoder

{

int n;//integer n

ShuffleCipher(int n)//constuctor that have one parameter

{

this.n=n;

}

private String OneShuffle(String s)//private method that shuffle the string on time

{

int len=s.length();//assign the length of the string s

int half,len1,len2,i;//variables

char c;//character c

String first_half="",second_half="",ans="";//variable first_half holds the first half of the string and second_half holds the second half of the string

if(len%2!=0)//if length of the string s is odd

{

half=(len/2) +1;

}

else//if it is even

half=len/2;

for(i=0;i<half;i++)//assign the first half of the string s to first_half

{

c = s.charAt(i);

first_half+=c;

}

int j=0;

for(i=half;i<len;i++)//assign the second half of the string s to first_half

{

c = s.charAt(i);

second_half+=c;

}

len1=first_half.length();//calculate the length of the first_half

len2=second_half.length();//calculate the length of the second_half

if(len1==len2)//if both length are same

{

for(i=0;i<len1;i++)

{

c = first_half.charAt(i);

ans+=c;

c = second_half.charAt(i);

ans+=c;

}

}

else//if both length are not same

{

for(i=0;i<len2;i++)

{

c = first_half.charAt(i);

ans+=c;

c = second_half.charAt(i);

ans+=c;

}

c = first_half.charAt(i);

ans+=c;//add the last character of the first_half

}

return ans;

}

public String encode( String plainText)//abstract method implementation

{

String ans="";//ans string that holds the shuffle string

ans=OneShuffle(plainText);//calling theOneShuffle

for(int i=0;i<n-1;i++)//if n is more the 1 then

{

ans=OneShuffle(ans);

}

return ans;

}

public static void main (String[] args)

{

Scanner input = new Scanner(System.in);//creates the object of the scanner class

System.out.print("Enter message : ");

String PlainText=input.nextLine();//taking plain text from the user

System.out.print("Enter no of shuffle : ");//taking shuffle from the user

int shuffle=input.nextInt();

ShuffleCipher t=new ShuffleCipher(shuffle);//creates the object of the class SubstitutionCipher

String s=t.encode(PlainText);//calling the method encode

System.out.println("\nShuffled message is :"+s);//prints the ans

}

}

output

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