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1. Inheritance

In OOP, one can also create a class that is based on another class.

• The parent class is called the superclass
• The new, child class is called the subclass

In this example, we make a base class Animal to serve as the superclass of a subclass Dog.

We say that a Dog is-a Animal.

For has-a relationships, we make those properties of the class (like has-a name).

class Animal {
    public void speak() {
        printf("I am an animal\n");
    }
}

|  Added class Animal

Animal animal = new Animal();

|  Added variable animal of type Animal with initial value Animal@44e81672

animal.speak();

I am an animal

class Dog extends Animal {
    public void speak() {
        printf("woof!\n");
    }    
}

|  Added class Dog

Dog dog = new Dog();

|  Added variable dog of type Dog with initial value Dog@2471cca7

dog.speak();

woof!

Animal whatisthis = dog;

|  Added variable whatisthis of type Animal with initial value Dog@2471cca7

whatisthis.speak();

woof!

The Dog object gets the message "speak" and it has a method for that.

This is called Polymorphism.

See Page 19 of your textbook for more details.