Java polymorphism: the secret weapon that makes objects flexible and changeable

In object-oriented programming, Java's polymorphism is a powerful feature that allows objects to exhibit flexible and changeable behavior. Through polymorphism, the same method can show different behaviors according to different object types, which brings great convenience to the flexibility and scalability of the code. In this article, PHP editor Xinyi will reveal the secret weapon of Java polymorphism and take you to have an in-depth understanding of this important programming concept so that it can be better applied in actual development.

1. Inheritance to achieve polymorphism

In Java, inheritance is the most common way to achieve polymorphism. When a class is derived from another class, the child class inherits all the properties and methods of the parent class. In addition, subclasses can also define their own properties and methods, thereby extending the functionality of the parent class.

Demo code:

class Animal { public void eat() { System.out.println("Animal is eating"); } } class Dog extends Animal { @Override public void eat() { System.out.println("Dog is eating"); } } public class Main { public static void main(String[] args) { Animal animal = new Dog(); animal.eat(); // 输出：Dog is eating } }

In this example, theDogclass inherits from theAnimalclass and overrides theeat()method. When we create aDogobject and assign it to aAnimalvariable, we can call theeat()method, but what is actually executed is ## Theeat()method in the #Dogclass.

2. Interface implementation polymorphism

Demo code:

interface Drawable { void draw(); } class Rectangle implements Drawable { @Override public void draw() { System.out.println("Drawing a rectangle"); } } class Circle implements Drawable { @Override public void draw() { System.out.println("Drawing a circle"); } } public class Main { public static void main(String[] args) { Drawable drawable = new Rectangle(); drawable.draw(); // 输出：Drawing a rectangle drawable = new Circle(); drawable.draw(); // 输出：Drawing a circle } }

Drawableinterface defines adraw()method, and both theRectangleandCircleclasses implement this interface. When we create aDrawableobject and assign it to aRectangleorCirclevariable, we can call thedraw()method, But what is actually executed is thedraw()method in theRectangleorCircleclass.

3. Benefits of polymorphism

Improve code reusability: Polymorphism allows us to use the same interface in different classes, thereby improving code reusability.
Improve code maintainability: Polymorphism makes code easier to maintain because we can change the behavior of the object by modifying methods in the subclass without having to modify methods in the parent class.
Improve the scalability of the code: Polymorphism makes the code easier to extend, because we can extend the functionality of the program by adding new subclasses without having to modify the existing code.

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