Chapter 8, Problem 16E

 Creation of the class “SubstitutionCipher”:

The creation of the derived class “SubstitutionCipher” is given below:

• • Declare the “s” variable.
• • Define the constructor with the parameter “shift”.
  • ○ Set the value to the declared variable.
• • The “encode” method is used to encode the given plain text.
  • ○ Declare the string variable “msg” with the empty string.
  • ○ The “for” loop iterate 0 to the length of the plain text.
    • ■ Declare and assign the character to “c” variable.
    • ■ Add the “msg” and “shift” value (by calling the “shift” method).
      • ○ Return the “msg” value.
• • The “shift” method is used to move the value to the number of moves the user entered in the main class.
  • ○ Declare the variable “ch” and assign the value.
  • ○ Check the “c” value is in the series of “a” to “z”.
    • ■ Shift the value after “c” value.
      • ○ Check the “c” value is in the series of “A” to “Z”.
        • ■ Shift the value after “c” value.
      • ○ Return the “msg” value.

 Filename: MessageEncoder.java

• • Declare the “encode” method along with the parameter “plainText”.
  • ○ This method take the string variable as plain text, then encodes and returns it as encoded message.

 Filename: Demo.java

• • Create a main class “Demo”.
  • ○ Define the main method.
    • ■ Create an object for the “s” for the scanner class.
    • ■ Get the plain text from the user.
    • ■ Get the shift value from the user.
    • ■ Call the “encode” method with the parameter “p”.
    • ■ Display the encoded text on the output screen.

 Program:

 Filename: SubstitutionCipher.java

//definition of "SubstitutionCipher" class

public class SubstitutionCipher implements MessageEncoder

{

    //declare the variable

    private int s;

    //definition of constructor

    public SubstitutionCipher (int shift)

    {

        //set the value

        s = shift;

    }

    //definition of "encode" method

    public String encode (String plainText)

    {

/*declare and set the empty string to the variable*/

        String msg = "";

        //check the condition

        for (int i = 0; i < plainText.length(); i++)

        {

/*declare the variable and assign the char */

            char c = plainText...