Add an abstract int avgBreedWeight() method to the Dog class. Remember that this means that the word abstract appears in the method header after public, and that the method does not have a body (just a semicolon after the parameter list). It makes sense for this to be abstract, since Dog has no idea what breed it is. Now any subclass of Dog must have an avgBreedWeight method; since both Yorkshire and Laborador do, you should be all set.
Save these changes and recompile DogTest.java. You should get an error in Dog.java (unless you made more changes than described above). Figure out what's wrong and fix this error, then recompile DogTest.java. You should get another error, this time in DogTest.java. Read the error message carefully; it tells you exactly what the problem is. Fix this by changing DogTest (which will mean taking some things out).
// ****************************************************************
// Dog.java
//
// A class that holds a dog's name and can make it speak.
//
// ****************************************************************
public class Dog
{
protected String name;
// ------------------------------------------------------------
// Constructor -- store name
// ------------------------------------------------------------
public Dog(String name)
{
this.name = name;
}
// ------------------------------------------------------------
// Returns the dog's name
// ------------------------------------------------------------
public String getName()
{
return name;
}
// ------------------------------------------------------------
// Returns a string with the dog's comments
// ------------------------------------------------------------
public String speak()
{
return "Woof";
}
}
// ****************************************************************
// Labrador.java
//
// A class derived from Dog that holds information about
// a labrador retriever. Overrides Dog speak method and includes
// information about avg weight for this breed.
//
// ****************************************************************
public class Labrador extends Dog
{
private String color; //black, yellow, or chocolate?
private int breedWeight = 75;
public Labrador(String name, String color)
{
this.color = color;
}
// ------------------------------------------------------------
// Big bark -- overrides speak method in Dog
// ------------------------------------------------------------
public String speak()
{
return "WOOF";
}
// ------------------------------------------------------------
// Returns weight
// ------------------------------------------------------------
public static int avgBreedWeight()
{
return breedWeight;
}
}
// ****************************************************************
// Yorkshire.java
//
// A class derived from Dog that holds information about
// a Yorkshire terrier. Overrides Dog speak method.
//
// ****************************************************************
public class Yorkshire extends Dog
{
public Yorkshire(String name)
{
super(name);
}
// ------------------------------------------------------------
// Small bark -- overrides speak method in Dog
// ------------------------------------------------------------
public String speak()
{
return "woof";
}
}
// ****************************************************************
// DogTest.java
//
// A simple test class that creates a Dog and makes it speak.
//
// ****************************************************************
public class DogTest
{
public static void main(String[] args)
{
Dog dog = new Dog("Spike");
System.out.println(dog.getName() + " says " + dog.speak());
}
}