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, the Dog class inherits from the Animal class and overrides the eat() method. When we create a Dog object and assign it to a Animal variable, we can call the eat() method, but what is actually executed is ## The eat() method in the #Dog class.

2. Interface implementation polymorphism

In Java, interfaces are also an important way to achieve polymorphism. An interface is a collection of methods that defines the behavior of an object, but does not define the state of the object. When a class implements an interface, it must implement all methods defined in the interface.

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
}
}

In this example, the

Drawable interface defines a draw() method, and both the Rectangle and Circle classes implement this interface. When we create a Drawable object and assign it to a Rectangle or Circle variable, we can call the draw() method, But what is actually executed is the draw() method in the Rectangle or Circle class.

3. Benefits of polymorphism

Polymorphism brings many benefits to Java, including:

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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