Question

- Class DiscountPolicy is an abstract class with a method called computeDiscount, which returns the discount for the purchase of items. DiscountPolicy knows the name of the item and its cost as well as the number of items being purchased.

- Class BulkDiscount, derived from DiscountPolicy, has two fields, minimum and percentage. computeDiscount method will return the discount based on the percentage applied, if the quantity of items purchased is more than minimum.
For example: if minimum is 3 and the number of items purchased is 5, then there will be 10% discount on the total amount.

- Class BuyNGet1Free, derived from DiscountPolicy, has a single field called n. computeDiscount method will compute discount so that every n^th item is free.
For example: for an item that costs $10 and when n is 3 -- purchase of 2 items results in no discount; purchase of 4 items results in a discount of $10, since the third item is free.

- The tester should create 10 different instances/objects of the classes, add them to an ArrayList of DiscountPolicy type. Do not create an object reference for each one. Tester should test the methods of classes and should show your knowledge of polymorphism.

Be sure to implement ALL classes as completely as a class should be, i.e. constructors, get, set, toString, and equals methods.

in java langauge

Answer 1

The provided problem will have 4 total files as below:

1. DiscountPolicy.java:

public abstract class DiscountPolicy {

                //instance variables

                private String itemName;

                private double cost;

                private int totalItemstoPurchase;

                public DiscountPolicy() {// default constructor

                }

                //parameterised constructor

                public DiscountPolicy(String itemName, double cost, int totalItemstoPurchase) {

                                this.itemName = itemName;

                                this.cost = cost;

                                this.totalItemstoPurchase = totalItemstoPurchase;

                }

                public abstract double computeDiscount();//abstract method to be implemented in derived classes

                // getters

                public int getTotalItemsToPurchase() {

                                return totalItemstoPurchase;

                }

                public double getItemCost() {

                                return cost;

                }

                public String getItemName() {

                                return itemName;

                }

                // setters

                void setTotalItemsToPurchase(int totalItemstoPurchase) {

                                this.totalItemstoPurchase = totalItemstoPurchase;

                }

                void setItemCost(double cost) {

                                this.cost = cost;

                }

                void setItemName(String itemName) {

                                this.itemName = itemName;

                }

                //equal return true when all variables has same value

                public boolean equals(Object obj) {

                                if (obj != null && obj.getClass() == getClass()) {

                                                return itemName == ((DiscountPolicy) obj).itemName && cost == ((DiscountPolicy) obj).cost

                                                                                && totalItemstoPurchase == ((DiscountPolicy) obj).totalItemstoPurchase;

                                }

                                return false;

                }

                public String toString() {//object details in string format

                                return "\n========================\nItem Name: " + itemName + "\nPer Item Cost: " + cost

                                                                + "\nTotal items to purchase: " + totalItemstoPurchase;

                }

}

2. BulkDiscount.java

public class BulkDiscount extends DiscountPolicy {

                private int minimum;

                private int percentage;

//parameterisation constructor

                public BulkDiscount(String itemName, double cost, int totalPurchase, int minimum, int percentage) {

                                super(itemName, cost, totalPurchase);

                                this.minimum = minimum;

                                this.percentage = percentage;

                }

                public BulkDiscount() {//default constructor

                }

                @Override

                public double computeDiscount() {

                                double totalAmount, discount = 0;

                                if (getTotalItemsToPurchase() > minimum) {

                                                totalAmount = getTotalItemsToPurchase() * getItemCost();

                                                discount = (totalAmount * percentage) / 100; // percentage% of totalAmount is discount

                                } // end if

                                return discount;// return final discount

                }

                // getter

                public int getMinimum() {

                                return minimum;

                }

                public int getPercentage() {

                                return percentage;

                }

                // setter

                public void setMinimum(int minimum) {

                                this.minimum = minimum;

                }

                public void setPercentage(int percentage) {

                                this.percentage = percentage;

                }             

                @Override

                public boolean equals(Object obj) { //check whether passed object is same as this object

                                if(obj instanceof BulkDiscount                ) {

                                                //if name, minimum and percentage is same , then object is same

                                                                return super.equals(obj) && minimum==((BulkDiscount) obj).minimum

                                                                                                &&percentage==((BulkDiscount) obj).percentage;

                                                }

                return false;

                }            

                @Override

                public String toString() {//call super's toString and add base class details

                                return super.toString() + "\nDiscount: " + computeDiscount() + "\nFinal Amount: "

                                                                + (getItemCost() * getTotalItemsToPurchase() - computeDiscount());

                }

}

3. BuyNGet1Free.java

public class BuyNGet1Free extends DiscountPolicy{

                private int n;

               

                public BuyNGet1Free() {}//default consurtuctor

                public BuyNGet1Free(String itemName, double cost, int totalItemstoPurchase, int n) {

                                super(itemName, cost, totalItemstoPurchase);

                                this.n=n;

                }

               

                @Override

                public double computeDiscount() {

                                double discount = 0;

                                if(getTotalItemsToPurchase()>=n) {//if items to be purchases is more than or equal to n

                                                discount = getItemCost(); //discount is qual to price of one item

                                }//end if

                                return discount;//return final discount

                }

                public void setN(int n) {//setter for n

                                this.n=n;

                }

                public int getN() {//getter to n

                                return n;

                }

                @Override

                public boolean equals(Object obj) { //check whether passed object is same as this object

                                if(obj instanceof BuyNGet1Free) {

                                                //if name, minimum and percentage is same , then object is same

                                                                return super.equals(obj) && n==((BuyNGet1Free) obj).n;

                                                }

                return false;

                }

                @Override

                public String toString() { //call super's to Stringand add base class details

                                return super.toString()+"\nMinimum units for Discount: "+n+

                                                                "\nDiscount: "+computeDiscount()+

                                                                "\nFinal Amount: "+(getItemCost()*getTotalItemsToPurchase()-computeDiscount());

                }

}

4.DriverDemo.java

public class DriverDemo {

                public static void main(String[] args) {

                                // create 5 objects of sub class BulkDiscount

                                DiscountPolicy d1 = new BulkDiscount("Item1", 10, 2, 2, 10);

                                DiscountPolicy d2 = new BulkDiscount("Item1", 10, 2, 2, 10);

                                DiscountPolicy d3 = new BulkDiscount("Item3", 4, 9, 5, 5);

                                DiscountPolicy d4 = new BulkDiscount("Item4", 3, 2, 4, 10);

                                BulkDiscount d5 = new BulkDiscount(); // one with default constructor to check setters

                                d5.setItemName("Item5");

                                d5.setItemCost(6);

                                d5.setTotalItemsToPurchase(10);

                                d5.setMinimum(5);

                                d5.setPercentage(8);

                                // create another 5 objects of sub class BuyNGet1Free

                                DiscountPolicy d6 = new BuyNGet1Free("Item6", 10, 2, 5);

                                DiscountPolicy d7 = new BuyNGet1Free("Item7", 5, 6, 6);

                                DiscountPolicy d8 = new BuyNGet1Free("Item8", 4, 9, 7);

                                DiscountPolicy d9 = new BuyNGet1Free("Item9", 3, 2, 8);

                                BuyNGet1Free d10 = new BuyNGet1Free(); // one with default constructor to check setters

                                d10.setItemName("Item10");

                                d10.setItemCost(6);

                                d10.setTotalItemsToPurchase(6);

                                d10.setN(4);

                                // create array of all objects

                                DiscountPolicy[] policyArray = { d1, d2, d3, d4, d5, d6, d7, d8, d9, d10 };

                                for (int i = 0; i < policyArray.length; i++) {// repeat for all objects

                                                System.out.println(policyArray[i]);// call toString method and print object details

                                }

                                System.out.println("\n==================\nCheck if first object " + d1.getItemName()

                                                                + " is equal to second object " + d2.getItemName());

                                System.out.println("\n==================\nFirst Object: " + d1);

                                System.out.println("\n==================\nSecond Object: " + d2);

                                if (d1.equals(d2))

                                                System.out.println("\n==================\nObjects are equal");

                                else

                                                System.out.println("\n==================\nObjects are not equal");

                }

}

OUTPUT: