Question

object oriented programming java homework question about abstracting and interfaces

2. Definition of a hierarchy of fruits is given below. • Fruit contains an abstract method getVitamin() that returns String. Fruit contains a String field color. Fruits are Apple, Banana, Strawberry and Blackberry. Apples are green, bananas are yellow, strawberries are red, blackberries are black. All these classes have zero parameter constructors. O Apple's vitamins are "A B12". 0 Banana's vitamins are "CD". O Strawberry's vitamins are “B5 E". 0 Blackberry's vitamins are "CK". Apples and bananas grow on trees. All tree fruits provide a void method named peel(). Define a class (or interface?) named TreeFruit that has method peel. Make Apple and Banana extend (or implement?) TreeFruit. o When an Apple is being peeled, it prints out “Peeling an apple.". o When a Banana is being peeled, it prints out "Peeling a banana.". Strawberries and blackberries grow on the ground. All ground fruits provide a void method named pick(). Define a class (or interface?) named GroundFruit that has method pick. Make Strawberry and Blackberry extend (or implement?) GroundFruit. o When a Strawberry is being picked, it prints out “Picking a strawberry." o When a Blackberry is being picked, it prints out “Picking a blackberry." a. Implement the classes. b. Implement a method named prepare Fruits that takes a list of fruits and invokes tree fruits' peel method and ground fruits' pick method. i.e. You have to distinguish tree fruits from ground fruits. public static void prepareFruits ArrayList<Fruit> fruits) { // IMPLEMENT THIS METHOD c. Use the following main method to test your code. public static void main(String[] args) { ArrayList<Fruit> fruits = new ArrayList<Fruit>(); fruits.add(new Apple(); fruits.add(new Banana(); fruits.add(new Strawberry(); fruits.add(new Blackberry(); prepareFruits(fruits);

Answer 1

/*
* Driver program that demonstrates the classes ,Fruit.java, TreeFruit.java, GroudFruit.java
* Apple.java
* Banana.java
* StrawBerry.java
* BlackBerry.java
* */
//Driver.java
import java.util.ArrayList;
public class Driver
{
   public static void main(String[] args)
   {
       ArrayList<Fruit> fruits=new ArrayList<Fruit>();
       fruits.add(new Apple());
       fruits.add(new Banana());
       fruits.add(new StrawBerry());
       fruits.add(new BlackBerry());
       //calling method ,prepareFruits
       prepareFruits(fruits);

   }
/*The method prepareFruits takes ArrayList of Fruit type
   * and then call the peel for the Apple and Banana
   * or pick for straw berry and blue berry */
   private static void prepareFruits(ArrayList<Fruit> fruits)
   {
       for (Fruit fruit : fruits)
       {
           //check if fruit is an instance of Apple then call
           //peel method
           if(fruit instanceof Apple)
               ((Apple) fruit).peel();
           //check if fruit is an instance of Apple then call
           //peel method
           else if(fruit instanceof Banana)
               ((Banana) fruit).peel();
           //check if fruit is an instance of StrawBerry then call
           //pick method
           if(fruit instanceof StrawBerry)
               ((StrawBerry) fruit).pick();
           //check if fruit is an instance of BlackBerry then call
           //pick method
           else if(fruit instanceof BlackBerry)
               ((BlackBerry) fruit).pick();
           System.out.println("Vitamins : "+fruit.getVitamin());      
       }
   }
}
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//Fruit.java
public abstract class Fruit
{
   public String color;
   public abstract String getVitamin();
}

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//TreeFruit.java
public interface TreeFruit
{
   public void peel();
}

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//GroundFruit.java
public interface GroundFruit
{
   public void pick();
}

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//Apple.java
public class Apple extends Fruit implements TreeFruit
{
   //Override peel method of the TreeFruit interface
   public void peel() {
       System.out.println("Peeling an apple");      
   }
   //Override getVitamin method of the Fruit abstract class
   public String getVitamin() {
       return "A B12";
   }
}

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//Banana.java
public class Banana extends Fruit implements TreeFruit
{
   //Override peel method of the TreeFruit interface
   public void peel() {
       System.out.println("Peeling a banana");      
   }
   //Override getVitamin method of the Fruit abstract class
   public String getVitamin() {
       return "C D";
   }
}

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//StrawBerry.java
public class StrawBerry extends Fruit implements GroundFruit
{
   //Override getVitamin method of the Fruit abstract class
   public String getVitamin() {
       return "B5 E";
   }
   //Override
   public void pick() {
       System.out.println("Picking a strawberry");      
      
   }
}

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

//BlackBerry.java
public class BlackBerry extends Fruit implements GroundFruit
{
   //Override getVitamin method of the Fruit abstract class
   public String getVitamin() {
       return "C K";
   }
   //Override
   public void pick() {
       System.out.println("Picking a blackberry");      

   }
}

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

Sample Output:

Peeling an apple Vitamins : A B12 Peeling a banana Vitamins: CD Picking a strawberry Vitamins : B5 E Picking a blackberry Vitamins : CK