HW 7

Assignment #7 - Inheritance and Interfaces

Due: Saturday, July 17

Do the following programming exercises:

Exercise 1

Write a class called Triangle that extends GeometricObject (Recall that this is one of the examples linked from the Inheritance notes set).

Filename should be Triangle.java
A triangle object should store the lengths of its three sides
Provide a constructor with three parameters, so that a triangle can be initialized when it is created. Sample creation:
```
 // a triangle with sides of length 4, 5, and 6
 Triangle t = new Triangle(4, 5, 6); 
```
implement the findArea and findPerimeter methods (recall these are abstract in class GeometricObect). The following is how to find the area of any triangle:
```
  s = (side1 + side2 + side3) / 2
  area = square root of (s * (s - side1) * (s - side2) * (s - side3))
```

Exercise 2

Create an interface named Eatable as follows:

  public interface Eatable
  {
    public String howToEat();
  }

Every class of an eatable object must implement the Eatable interface. Create the following sets of classes:

Create a class called Animal, with subclasses Tiger, Chicken, and Elephant. Since chicken is eatable, implement the Eatable interface for the Chicken class.
Create a class called Fruit, with subclasses Apple and Orange. Since all fruits are eatable, implement the Eatable interface for the Fruit class. In the Fruit class, give a generic implementation of the howToEat method. In the Apple and Orange classes, give specific implementations of this method.

Override the toString method in each class to return the name of the class.

For each class that implements Eatable, the howToEat method needs to be defined to return the eating instructions (as a String).

You can use the following main program to test:

The EatingTest class

EatingTest.java

public class EatingTest
{
    public static void main(String[] args)
    {
        Object[] objects = 
            {  new Object(), new Animal(), new Tiger(), new Chicken(), 
               new Elephant(), new Fruit(), new Apple(), 
               new Orange()
            };

        for (int i = 0; i < objects.length; i++)
        {
            showObject(objects[i]);
        }
    }

    public static void showObject(Object object)
    {
        System.out.print(object);
        if (object instanceof Eatable)
        {
            System.out.print(((Eatable)object).howToEat());
        }
        System.out.println();
    }
}

Sample run of main program

 java.lang.Object@f4a24a
 Animal
 Tiger
 Chicken (pluck then cook)
 Elephant
 Fruit (eat raw)
 Apple (polish)
 Orange (peel)

Note: The toString() method for class Object (the base class version) returns a string consisting of the name of the class, the '@' symbol, and the hash code of the object (in hexadecimal format). Your output for the toString() method of the Object instance may not look exactly like mine.

Submitting

Pack up all your source code files with jar. This does not need to be a "runnable" jar file (so no manifest addition needed). (Jarfile is hw7.jar).

E-mail this jar file to me (myers@cs.fsu.edu) by the due date. Your e-mail subject should be HW7-SUBMIT. Include your name and section in the e-mail body. Please only submit ONCE, unless you make a mistake and need to correct it (before the due date) -- and minimize this. Only the last submission will be graded.