Question

Part A: (Chapter 8) Make the following updates to the original code below:

• Override the toString() method and equals() method inside your class [2 points]
• Create a Copy Constructor in your class [2 point]
• Create a static field in your class called counter. It should increment every time an object is created. [1 point]
• Create a static method that displays the counter value. Also call this method at the end of your main method. [1 point]
• Use the "this" reference in all your setter (mutator) methods and also use the "this" reference in your default constructor to call the parameterized constructor. [1 point]
• Demonstrate that the copy Constructor, toString, and equals methods work in your main method [2 point]

Part B : (Chapter 10) Make the following updates to your Assignment 1

• Create a sub class that inherits everything from your base class. (For example, if Car is the base class then SportsCar could be your sub class) [1 point]
• Provide at least one additional attribute to your subclass [1 point]
  • Create gettter/setter methods for it.
• Create a default constructor for the subclass, that uses super to call the base class default constructor. [1 point]
  • It should set all attributes in the subclass as well as the super class to default values
• Create a parameterized constructor for the subclass, that uses keyword super to pass the inherited parameters to the base class. [2 point]
  • It should set all attributes in the subclass as well as the super class to the values that are passed in to the constructor.
• Override the display() method to print out all the instance variable values from the base class, and also from the sub class. [2 point]
• In your main method, create 2 new object using your subclass, set the data, and call the display method.
  • Create one object using the no-arg (default) constructor of your sub-class. [1 point]
    • Call the set methods to set all attribute data associated to that object.
    • Call the display method for that object
  • Create one object using the parameterized constructor of your sub-class. [1 point]
    • Call the display() method for this object too
• Add all these objects from Assignment 2 to the same array you created in Assignment 1, and loop through all objects to call the display method. (This demonstrates polymorphism)  [2 point]

----

Original Code:

public class Coffee {
    private int Number;
    private double price;
    private String title;

    public Coffee() {
    }

    public Coffee (int Number, double price, String title) {
        this.Number = Number;
        this.price = price;
        this.title = title;
    }

    public void display() {
        System.out.println("Coffee [price=" + this.price + ", title=" + this.title + ", Number=" + this.Number + "]");
    }

    public String getTitle() {
        return this.title;
    }

    public void setTitle(String title) {
        this.title = title;
    }

    public int getNumber() {
        return this.Number;
    }

    public void setNumber(int Number) {
        this.Number = Number;
    }

    public double getPrice() {
        return this.price;
    }

    public void setPrice(double price) {
        this.price = price;
    }
}

-----

Driver (demo) code:

public class Driver {

        public static void main(String[] args) {
            Coffee C1 = new Coffee();
            C1.setPrice(2.50);
            C1.setTitle("Black");
            C1.setNumber(1);
            System.out.println("C1:");
            C1.display();

            Coffee C2 = new Coffee (2, 6.00, "Latte");
            System.out.println("\nC2:");
            C2.display();
        }
}

---------------

Result:

C1: Coffee [price=2.5, title=Black, Number=1]

C2: Coffee [price=6.0, title=Latte, Number=2]

Process finished with exit code 0

Answer 1

Find below the java code that meets all the Assignment conditions and all points are properly described using comments.

Java Code:

class Coffee {
        private int Number;
        private double price;
        private String title;
        private static int counter;

        // increment every time when object is created
        {
                counter += 1;
        }

        // static method that displays the counter value
        public static void displayCounter() {
                System.out.println("\nCounter: " + counter);
        }

        public Coffee() {
                this(0, 0, null); // "this" reference to call the parameterized constructor
        }

        public Coffee(int Number, double price, String title) {
                this.Number = Number;
                this.price = price;
                this.title = title;
        }

        // copy constructor
        public Coffee(Coffee coffee) {
                this.Number = coffee.Number;
                this.price = coffee.price;
                this.title = coffee.title;
        }

        public void display() {
                System.out.println("Coffee [price=" + this.price + ", title=" + this.title + ", Number=" + this.Number + "]");
        }

        public String getTitle() {
                return this.title;
        }

        public void setTitle(String title) {
                this.title = title;
        }

        public int getNumber() {
                return this.Number;
        }

        public void setNumber(int Number) {
                this.Number = Number;
        }

        public double getPrice() {
                return this.price;
        }

        public void setPrice(double price) {
                this.price = price;
        }

        // override equals methods of Coffee class
        @Override
        public boolean equals(Object o) {
                // If the object is compared with itself then return true
                if (o == this) {
                        return true;
                }

                /*
                 * Check if o is an instance of Complex or not "null instanceof [type]" also
                 * returns false
                 */
                if (!(o instanceof Coffee)) {
                        return false;
                }

                // typecast o to Coffee so that we can compare data members
                Coffee c = (Coffee) o;

                // Compare the data members and return accordingly
                return Double.compare(price, c.price) == 0 && Integer.compare(Number, c.Number) == 0 && title.equals(c.title);
        }
        
        // override toString methods of Coffee class
        @Override
        public String toString() {
                return "Coffee [Number=" + Number + ", price=" + price + ", title=" + title + "]";
        }

}

// subclass that extends Coffee class
class PremiumCoffee extends Coffee {
        private boolean premium; // one additional attribute of subClass

        // default constructor
        public PremiumCoffee() {
                super();                        // call base class default constructor
                premium = false;
        }

        public PremiumCoffee(boolean premium, int Number, double price, String title) {
                super(Number, price, title);            // call base class parameterized constructor
                this.premium = premium;

        }
        
        /*
         * Override the display() method to print out all the instance variable
         * values from the base class, and also from the sub class 
         */
        @Override
        public void display() {
                System.out.println("PremiumCoffee [price=" + getPrice() + ", title=" + getTitle() + ", Number=" + getNumber() + ", Premium=" + this.premium + "]");
        }
        

        public boolean isPremium() {
                return premium;
        }

        public void setPremium(boolean premium ) {
                this.premium = premium;
        }
        
}

public class Driver {

        public static void main(String[] args) {
                
                // using the no-arg (default) constructor
                Coffee C1 = new Coffee();
                C1.setPrice(2.50);
                C1.setTitle("Black");
                C1.setNumber(1);
                System.out.println("C1:");
                C1.display();
                
                // creating object using copy Constructor 
                Coffee C2 = new Coffee(C1);
                System.out.println("\nCopy Constructor(C2):");
                C2.display();
                // check overriden methods toString() and equals()
                System.out.println("\ntoString() : "+C2);
                System.out.println("Is C1 is equals to C2? "+C1.equals(C2));
                
                //using the parameterized constructor
                Coffee C3 = new Coffee(2, 6.00, "Latte");
                System.out.println("\nC3:");
                C3.display();
                System.out.println("Is C1 is equals to C3? "+C1.equals(C3));
                
                // using the no-arg (default) constructor
                PremiumCoffee PC1 = new PremiumCoffee();
                PC1.setPrice(5.50);
                PC1.setTitle("AMERICANO");
                PC1.setNumber(3);
                PC1.setPremium(true);
                System.out.println("\nPC1:");
                PC1.display();
                
                //using the parameterized constructor
                PremiumCoffee PC2 = new PremiumCoffee(false, 4, 8.00, "CAPPUCCINO");
                System.out.println("\nPC2:");
                PC2.display();
                
                // call displayCounter() to get the total number of objects created
                Coffee.displayCounter();
                
        }
}