Question

When your program is correctly run, it will be provided two strings: the encrypted message and a string that is in the deciphered text. If fewer/more arguments are provided, your program is to output an error:

$ java edu.wit.cs.comp1050.PA4a

Please supply correct inputs: : <encrypted string> <substring>

$ java edu.wit.cs.comp1050.PA4a a

Please supply correct inputs:  : <encrypted string> <substring>

$ java edu.wit.cs.comp1050.PA4a a b c

Please supply correct inputs:  : <encrypted string> <substring>

If the correct arguments are supplied, you are to output any shifts (00-25) that contain the supplied substring:

$ java edu.wit.cs.comp1050.PA4a 'Jvtwbaly zjplujl pz mbu!' is

09: Secfkjuh isyudsu yi vkd!

19: Computer science is fun!

$ java edu.wit.cs.comp1050.PA4a 'Jvtwbaly zjplujl pz mbu!' 'fun!'

19: Computer science is fun!

If no shifts contain the substring, provide an error:

$ java edu.wit.cs.comp1050.PA4a 'Jvtwbaly zjplujl pz mbu!' '?'

No valid shifts found.

To build this program in an object-oriented fashion, you must first implement a Shifter class. This class is constructed with the encrypted string, and then has methods to both shift by an arbitrary amount and find substrings across all shifts.

To implement this class in an efficient manner, you should use a StringBuilder to shift the encrypted string. You might also find it useful to use an ArrayList to accumulate an unknown number of valid shifts. Look to the JavaDoc’s of the String class for methods to search a string for a substring.

Heres the skeleton code for PA4a

package edu.wit.cs.comp1050;

//TODO: document this class

public class PA4a {

/**

* Error if incorrect command-line arguments are supplied

*/

public static final String ERR_USAGE = "Please supply correct inputs: <encrypted string> <substring>";

/**

* Error if shift could not be found

*/

public static final String ERR_NONE = "No valid shifts found.";

/**

* Outputs all shifts of the encrypted string

* that contain the supplied substring

* 

* @param args command-line arguments: <encrypted string> <substring>

*/

public static void main(String[] args) {

// replace with your code

}

}