Java Polymorphism: Understanding the Nature of Superclasses and the Art of Implementation

Java Polymorphism is an important concept in object-oriented programming, and mastering it is crucial to improving the flexibility and scalability of your code. PHP editor Youzi will take you to deeply explore the nature and implementation methods of Java polymorphism, helping you better understand the role of super classes and the art of polymorphism, so that you can be comfortable in Java programming.

In Java, superclass refers to the parent class of the derived class. Superclasses provide common behaviors and properties to derived classes, and derived classes can inherit and extend superclasses.

The main functions of super class are:

• Define public behaviors and properties for derived classes to inherit.
• Provide abstract methods so that derived classes can implement their own specific behavior.
• Define protected access permissions so that derived classes can access protected members of the superclass.
• Define final methods so that derived classes cannot override the behavior of superclasses.

The Art of Polymorphic Implementation

The implementation of polymorphism mainly relies on inheritance and method rewriting. Inheritance allows a derived class to inherit behaviors and properties from a superclass, while method overriding allows a derived class to modify inherited methods in the superclass.

The art of polymorphic realization is reflected in the following aspects:

• Derived classes can override superclass methods and provide their own specific implementations.
• Derived classes can call methods of the super class or methods they override.
• Derived class objects can be assigned to superclass variables, and methods can be called using references of the superclass type.

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.");
}
}

class Cat extends Animal {
@Override
public void eat() {
System.out.println("Cat is eating.");
}
}

public class Main {
public static void main(String[] args) {
Animal animal = new Dog();
animal.eat(); // prints "Dog is eating."

Animal anotherAnimal = new Cat();
anotherAnimal.eat(); // prints "Cat is eating."
}
}

In this code, both the Dog and Cat classes inherit the Animal class and override the eat() method. When the animal variable is assigned to the Dog object, calling the eat() method will print "Dog is eating." And when anotherAnimal variable is assigned to the Cat object, calling the eat() method will print "Cat is eating.".

Conclusion

Polymorphism is an important feature of Object-oriented programming in Java, which allows subclass objects to be referenced and used as superclass types. Through inheritance and method overriding, polymorphism allows derived classes to extend and modify the behavior and properties of superclasses.

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