Question

1. A company that wants to send data over the Internet will use an encryption program to ensure data security. All data will be transmitted as four-digit integers. The application should read a four-digit integer entered by the user and encrypt it as follows:  Replace each digit with the remainder of the new value divided by 10 by adding 6 to the digit. Then replace the number in the first digit with the third, and the number in the second digit with the fourth. Print the encrypted integer on the screen.  Write a separate application where an encrypted four-digit integer is entered and decrypted (reversing the encryption scheme) and finds the original number. 2. Create a class called Employee that contains three instance variables (First Name (String), Last Name (String), Monthly Salary (double)). Create a constructor that initializes these variables. Define set and get methods for each variable. If the monthly salary is not positive, do not set the salary. Create a separate test class called EmployeeTest that will use the Employee class. By running this class, create two employees (Employee object) and print the annual salary of each employee (object). Then set the new salary by giving each employee a 10% raise and display each employee's annual salary on the screen again.

Note: code should be written in Java language.

Answer 1

Answer 1:

package Security;

// Defines class Encrypt
class Encrypt
{
   // Method to encrypt the parameter plainNumber and returns it
   int encryptDigit(int plainNumber)
   {
       int one, two, three, four, swapNo;
       int encryptNumber = 0;
       // Calculates the quotient, adding 6 to it and then gets the remainder
       one = (plainNumber / 1000 + 6) % 10;
       two = (plainNumber % 1000 / 100 + 6) % 10;
       three = (plainNumber % 1000 % 100 / 10 + 6) % 10;
       four = (plainNumber % 1000 % 100 % 10 + 6) % 10;
      
       // Swapping process
       swapNo = one;
       one = three * 1000;
       three = swapNo * 10;
       swapNo = two;
       two = four * 100;
       four = swapNo * 1;
       encryptNumber = one + two + three + four;
       // Returns the encrypted number
       return encryptNumber;
   }// End of method
}// End of class Encrypt

// Defines class Decrypt
class Decrypt
{
   // Method to decrypt the parameter encryptNumber and returns it
   int decryptDigit(int encryptNumber)
   {
       int first, second, third, fourth, decryptedNumber, temp;
       // Calculates the quotient
       first = encryptNumber / 1000;
       second = encryptNumber % 1000 / 100;
       third = encryptNumber % 1000 % 100 / 10;
       fourth = encryptNumber % 1000 % 100 % 10;
      
       // Swapping process
       temp = ( first + 4) % 10;
       first = ( third + 4) % 10;
       third = temp;
       temp = ( second + 4) % 10;
       second = ( fourth + 4) % 10;
       fourth = temp;
       decryptedNumber = first * 1000 + second * 100 + third * 10 + fourth;
       // Returns the decrypted number
       return decryptedNumber;
   }// End of method
}// End of class Decrypt

// Driver class definition
public class EncryptDecryptDigit
{
   // main method definition
   public static void main(String []s)
   {
       // Creates an object of class Encrypt
       Encrypt e = new Encrypt();
       // Creates an object of class Decrypt
       Decrypt d = new Decrypt();
      
       // Calls the method to encrypt
       int encryptNumber = e.encryptDigit(1234);
       System.out.println("\n Original Number: 1234" +
       "\n Encrypted Number: " + encryptNumber);
      
       // Calls the method to decrypt
       int decryptNumber = d.decryptDigit(encryptNumber);
       System.out.println("\n Encrypted Number: " + encryptNumber +
       "\n Decrypted Number: " + decryptNumber);
   }// End of main method
}// End of driver class

Sample Output:

Original Number: 1234
Encrypted Number: 9078

Encrypted Number: 9078
Decrypted Number: 1234
------------------------------------------------------------------------------------------------------------------------

// Defines class Employee
class Employee
{
   // Instance variables to store employee information
   String firstName;
   String lastName;
   double monthlySalary;
  
   // Parameterized constructor to assign parameter values to instance variables
   Employee(String firstName, String lastName, double monthlySalary)
   {
       this.firstName = firstName;
       this.lastName = lastName;
       setMonthlySalary(monthlySalary);
   }
  
   // Getter methods
   String getFirstName()
   {
       return firstName;
   }
   String getLastName()
   {
       return lastName;
   }
   double getMonthlySalary()
   {
       return monthlySalary;
   }
  
   // Setter methods
   void setFirstName(String firstName)
   {
       this.firstName = firstName;
   }
   void setLastName(String lastName)
   {
       this.lastName = lastName;
   }
   void setMonthlySalary(double monthlySalary)
   {
       // Checks if parameter monthlySalary is negative
       if(monthlySalary < 0)
           // Then assign 0.0
           monthlySalary = 0.0;
       // Otherwise assign parameter value
       else
           this.monthlySalary = monthlySalary;
   }
}// End of class Employee

// Driver class definition EmployeeTest
public class EmployeeTest
{
   // main function definition
   public static void main(String []s)
   {
       // Creates object of class Employee using parameterized constructor
       Employee emp1 = new Employee("Pyari", "Sahu", 5000);
       Employee emp2 = new Employee("Sasmita", "Panda", 3000);
      
       // Calculates and display annual salary
       System.out.println("\n Employee " + emp1.getFirstName() + " "
               + emp1.getLastName() + " annual Salary: $" +
               (emp1.getMonthlySalary() * 12.0));
      
       System.out.println("\n Employee " + emp2.getFirstName() + " "
               + emp2.getLastName() + " annual Salary: $" +
               (emp2.getMonthlySalary() * 12.0));

       // Sets 10% hide of monthly salary
       emp1.setMonthlySalary(emp1.getMonthlySalary() + (emp1.getMonthlySalary() * 0.10));
       emp2.setMonthlySalary(emp1.getMonthlySalary() + (emp1.getMonthlySalary() * 0.10));
      
       System.out.println("\n After 10% hike \n");
       // Calculates and display annual salary
       System.out.println("\n Employee " + emp1.getFirstName() + " "
               + emp1.getLastName() + " annual Salary: $" +
               (emp1.getMonthlySalary() * 12.0));
              
       System.out.println("\n Employee " + emp2.getFirstName() + " "
               + emp2.getLastName() + " annual Salary: $" +
               (emp2.getMonthlySalary() * 12.0));
   }// End of main method
}// End of driver class

Sample Output:

Employee Pyari Sahu annual Salary: $60000.0

Employee Sasmita Panda annual Salary: $36000.0

After 10% hike

Employee Pyari Sahu annual Salary: $66000.0

Employee Sasmita Panda annual Salary: $72600.0