Lab 6: Inheritance and Interfaces

Interfaces Problem Statement

Compulsorily use the concepts of interfaces to solve this problem. Failure to abide by this rule will result in zero marks.

Create an interface Encryption that has two methods: encrypt() and decrypt(). This form of encryption deals with encrypting strings.

There are two standards of encryption: FooEncryption, and BarEncryption. These will be represented as classes implementing Encryption.

FooEncryption of a string s can be defined by the following equation:

s[i] -> ascii_char(ascii_number(s[i]) - (i % 2) + 3)

BarEncryption of a string s can be defined by the following equation:

s[i] -> ascii_char((ascii_number(s[i]) - ascii_number(s[i-1]) + 80) if i >= 1, else

s[i] -> s[i]

The input will be given to you as follows:

<encryption type: foo or bar> <encrypt or decrypt: en or de> <input string>

Examples:

• foo en HELLOWORLD
• bar de HELLOWORLD

Constraints:

• 1 <= length(input_string) <= 65
• input_string consists of only capital letters.

Output must be the output string of either encryption or decryption using the standard specified in the input

Example outputs:

• KGONRYRTOF
• H9DAKSNYKF

Code

import java.io.*;
import java.util.*;
import java.text.*;
import java.math.*;
import java.util.regex.*;

interface Encryption {
    public void encrypt();
    public void decrypt();
}

class FooEncryption implements Encryption {
    String str;
    
    FooEncryption(String str) {
        this.str = str;
    }
    
    public void encrypt() {
        String res = "";
        for(int i = 0; i < this.str.length(); ++i) {
            char c = (char) (((int) this.str.charAt(i)) - (i % 2) + 3);
            res = res + c;
        }
        this.str = res;
    }
    
    public void decrypt() {
        String res = "";
        for(int i = 0; i < this.str.length(); ++i) {
            char c = (char) (((int) this.str.charAt(i)) + (i % 2) - 3);
            res = res + c;
        }
        this.str = res;
    }
}

class BarEncryption implements Encryption {
    String str;
    
    BarEncryption(String str) {
        this.str = str;
    }
    
    public void encrypt() {
        String res = String.valueOf(this.str.charAt(0));
        for(int i = 1; i < this.str.length(); ++i) {
            char c = (char) (((int) this.str.charAt(i)) - ((int) this.str.charAt(i - 1)) + 80);
            res = res + c;
        }
        this.str = res;   
    }
    
    public void decrypt() {
        String res = String.valueOf(this.str.charAt(0));
        for(int i = 1; i < this.str.length(); ++i) {
            char c = (char) (((int) this.str.charAt(i)) + ((int) this.str.charAt(i - 1)) - 80);
            res = res + c;
        }
        this.str = res;   
    }
}

public class Solution {
    public static void main(String[] args) {
        Scanner s = new Scanner(System.in);
        String input = s.nextLine();
        String fb = input.split(" ")[0], ed = input.split(" ")[1], str = input.split(" ")[2];
        if(fb.equals("foo")) {
            FooEncryption x = new FooEncryption(str);
            if(ed.equals("en")) {
                x.encrypt();
                System.out.println(x.str);
            }
            else {
                x.decrypt();
                System.out.println(x.str);
            }
        }
        else {
            BarEncryption x = new BarEncryption(str);
            if(ed.equals("en")) {
                x.encrypt();
                System.out.println(x.str);
            }
            else {
                x.decrypt();
                System.out.println(x.str);
            }
        }
    }
}