Java Polymorphism
Polymorphism means “many forms”, It is useful for code reusability: reuse attributes and methods of an existing class when you create a new class. It occurs when we have many classes that are related to each other by inheritance. Like we definite in the previous chapter; 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 diverse ways.
For example, think of a superclass called Tree that has a method called treeSound(). Subclasses of Tree could be SmallTree, MidSizeTree. And they also have their own implementation of an tree sound:
Example
class Tree {
public void treeSound() {
System.out.println(“The tree makes a sound in wind”);
}
}
class SmallTree extends Tree {
public void treeSound() {
System.out.println(“The SmallTree can also makes a sound in wind”);
}
}
class MidSizeTree extends c {
public void treeSound() {
System.out.println(“The MidSizeTree can also makes a sound in wind”);
}
}
Remember from the Inheritance chapter that we use the extends keyword to inherit from a class.Now we can create Pig and Dog objects and call the animalSound() method on both of them:
Example
class Tree {
public void treeSound() {
System.out.println(“The tree makes a sound in wind”);
}
}
class SmallTree extends Tree {
public void treeSound() {
System.out.println(“The SmallTree can also makes a sound in wind”);
}
}
class MidSizeTree extends c {
public void treeSound() {
System.out.println(“The MidSizeTree can also makes a sound in wind”);
}
}
class Main {
public static void main(String[] args) {
Tree myTree = new Tree(); // create Tree obj
Tree mySmall = new SmallTree();// create SmallTree obj
Tree myMidSize = new MidSizeTree();// create MidSizeTree obj
myTree.treeSound();
mySmall.treeSound();
mymyMidSize.treeSound();
}
}
OUTPUT
The tree makes a sound in wind
The SmallTree makes a sound in wind
The MidSizeTree can also makes a sound in wind