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:
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