![class MyMainClass {
public static void main(String[] args) {
Animal myAnimal = new Animal(); // Create an Animal object
Animal myPig = new Pig(); // Create a Pig object
Animal myDog = new Dog(); // Create a Dog object
myAnimal.animalSound();
myPig.animalSound();
myDog.animalSound();
}
}](https://image.slidesharecdn.com/inheritancepolymorphism-191114172017/85/Inheritance-Polymorphism-8-320.jpg)
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Inheritance & Polymorphism
- 2. Inheritance & OOP • In java inheritance means deriving a class from existing class. • This allows us to reuse code. • We can use fields & methods from the existing class, because it is reusable. • For example, the child inherits from his/her parents. • The existing class called super class & the deriving class called subclass. o Subclass (child): the class that inherits from another class o Super class (parent): the class being inherited from
- 3. The Object Class • As we will see, we can derive one class from another. For example, suppose we write a class called Product for a sports shop. • Basketball is a Product but is more specific than simply a Product. • So, we can say following: o Product is a class and has functionality that any products have. o Basketball is a class and has all the functionality of a Product but perhaps more. • So, the product is a super/base/parent class and the basketball is a child/sub class.
- 4. Example of Inheritance • Polygon is the base/super/parent class. Learn these 3 terms!! o Triangle “is a” Polygon and Rectangle “is a” Polygon. o Square “is a” special Rectangle. • We programming types use these terms: o base, super or parent class o child, sub, or derived class o is a
- 5. Polymorphism • Polymorphism is the ability of an object to take on many forms. • It allows us to call superclass method from a derived class because of the “is a” relationship. • We showed that inheritance lets us inherit attributes and methods from another class. Polymorphism uses those methods to perform different tasks. This allows us to perform a single action in different ways. • For example: public interface Vegetarian{} public class Animal{} public class Deer extends Animal implements Vegetarian{} • Now, the Deer class is polymorphic since this has multiple inheritance. Following are true for the above examples: A Deer IS-A Animal A Deer IS-A Vegetarian A Deer IS-A Deer A Deer IS-A Object
- 6. Example of Polymorphism • Superclass called Animal that has a method called animalSound(). Subclasses of Animals could be Pigs, Cats, Dogs; And they also have their own implementation of an animal sound (the pig oinks, cat meows, etc.): class Animal { public void animalSound() { System.out.println("The animal makes a sound"); } } class Pig extends Animal { public void animalSound() { System.out.println("The pig says: wee wee"); } } class Dog extends Animal { public void animalSound() { System.out.println("The dog says: bow wow"); } }
- 7. • Now we can create Pig and Dog objects and call the animalSound() method on both of them: • For Example: class Animal { public void animalSound() { System.out.println("The animal makes a sound"); } } class Pig extends Animal { public void animalSound() { System.out.println("The pig says: wee wee"); } } class Dog extends Animal { public void animalSound() { System.out.println("The dog says: bow wow"); } } Continued to next page . . .
- 8. class MyMainClass { public static void main(String[] args) { Animal myAnimal = new Animal(); // Create an Animal object Animal myPig = new Pig(); // Create a Pig object Animal myDog = new Dog(); // Create a Dog object myAnimal.animalSound(); myPig.animalSound(); myDog.animalSound(); } }