Creating a Polymorphism and Histogram Application in Java

Problem:

User

- username : String - password : String - items[] : String

+ User(username : String, password : String, items[] : String) + setUsername(username : String) : void + getUsername() : String + setPassword(password : String) : void + getPassword() : String + setItems(items[] : String) : void + getItems() : String[] # abstract getAccessibleItems() : String[] + toString() : String

Admin

+ Admin(username : String, password : String, items[] : String) + getAccessibleItems() : String[] + toString() : String

AccountingUser

+ AccountingUser(username : String, password : String, items[] : String) + getAccessibleItems() : String[] + toString() : String

In this assignment, you will be using inheritance and polymorphism to create an admin and an accounting user for some system.

The User class is an abstract class made up of a username, a password, and an array of accessible items. It has setter and getter methods and an abstract method called getAccessibleItems which should be implemented by subclasses of User.

The Admin class and the AccountingUser class are both subclasses of User. This means that you have to use inheritance to create both classes. Each of these classes' constructors must call the superclass constructor. Moreover, both of these classes have to implement the getAccessibleItems method which has to return an array of strings describing the items the user has access to.

Usually, a system admin has access to every item, while another user has access for a limited set of items. For example, the AccountingUser will have access to an accounting related item but not any other item.

Write a tester class which has an array of Users.

The array should contain one Admin and two AccountingUsers. After creating the users, you should loop over the array and use polymorphism to get the accessible items and print the user’s information.

Printing format is as follows:

(username)

Accessible items:

(getAccessibleItems())

Solution:

/**---------------AccountingUser.java--------------*/
public class AccountingUser extends User {

 public AccountingUser(String username, 
                  String password, String[] items) {
  super(username, password, items);
 }

 protected String[] getAccessibleItems() {
  String[] myItems = new String[2];
  
  myItems[0] = "Accounting View";
  myItems[1] = "Invoice View";
  
  return myItems;
 }
}

/**--------------Admin.java--------------------*/
public class Admin extends User {

 public Admin(String username, 
                   String password, String[] items) {
  super(username, password, items);
 }

 protected String[] getAccessibleItems() {
  return getItems();
 }
}
/**--------------User.java--------------------*/
public abstract class User {
 
 private String   username;
 private String   password;
 private String[] items;
 
 public User(String username, String password, 
                                      String[] items) {
  this.username = username;
  this.password = password;
  this.items = items;
 }

 public String getUsername() {
  return username;
 }

 public void setUsername(String username) {
  this.username = username;
 }

 public String getPassword() {
  return password;
 }

 public void setPassword(String password) {
  this.password = password;
 }

 public String[] getItems() {
  return items;
 }

 public void setItems(String[] items) {
  this.items = items;
 }

 protected abstract String[] getAccessibleItems();
 
 public String toString() {
  return username+"\n\n";
 }
 
}
/**------------------------Tester.java---------------------*/
public class Tester {

 public static void main(String[] args) {
  
  String[] items = {"Accounting view", 
                "Invoice view", "HR view", "Admin view", 
                "Marketing view", "IT view"};
  
  User[] users = new User[3];
  
  users[0] = new Admin("admin", "admin", items);
  users[1] = new AccountingUser("AccUser", "acc123", items);
  users[2] = new AccountingUser("AccUser2", "123acc", items);
  
  for (int i = 0; i < users.length; i++) {
   
   if(users[i] instanceof Admin) {
    
   Admin currentUser = (Admin) users[i];
   String[] accessibleItems = currentUser.getAccessibleItems();
   System.out.println(currentUser+"Accessible Items:");
   for (int j = 0; j < accessibleItems.length; j++)
   System.out.print(accessibleItems[j] + " ");
    
   } else {
    
   AccountingUser currentUser = (AccountingUser) users[i];
   String[] accessibleItems = currentUser.getAccessibleItems();
   System.out.println(currentUser+"Accessible Items:");
    
   for (int j = 0; j < accessibleItems.length; j++)
    System.out.print(accessibleItems[j] + " ");
   }
  }
 }
}