Java Inheritance

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Introduction to Inheritance in Java

Inheritance is a key principle of Object-Oriented Programming (OOP) in Java. This fundamental concept allows us to create new classes using existing classes. The goal of inheritance is to promote the reuse of code, simplify the creation of related classes, and establish a type hierarchy for objects.

What is Inheritance?

Inheritance in Java is a mechanism where a new class is derived from an existing class. The existing class is known as the superclass or parent class, and the newly created class is referred to as the subclass or child class.

The child class inherits all the states (attributes) and behaviors (methods) of the parent class, and can also add its own unique states and behaviors.

Syntax of Inheritance

In Java, the extends keyword is used to establish inheritance relationship between two classes. Here's a basic syntax of how to use it:

class Subclass extends Superclass{
  // fields and methods
}

In the above syntax, Subclass is the new class we're creating (child class), and Superclass is the existing class from which we're inheriting (parent class).

Example of Inheritance

Let's illustrate inheritance with a simple example. Suppose we have a superclass Animal and a subclass Dog.

class Animal {
  void eat() {
    System.out.println("The animal eats");
  }
}

class Dog extends Animal {
  void bark() {
    System.out.println("The dog barks");
  }
}

In this example, Dog class inherits the eat() method from Animal class. Now, we can create an object of Dog class and call both eat() and bark() methods.

class Main {
  public static void main(String[] args) {
    Dog dog = new Dog();
    dog.eat();
    dog.bark();
  }
}

When you run the program, you'll see this output:

The animal eats
The dog barks

This shows that the Dog class has successfully inherited from the Animal class.

Types of Inheritance

Java supports four types of inheritance:

1. Single Inheritance: When a class extends another single class.
2. Multilevel Inheritance: When a class extends a class, which extends another class.
3. Hierarchical Inheritance: When a single class is extended by multiple classes.
4. Hybrid Inheritance: A combination of more than one types of inheritance.

Note: Java does not support multiple inheritance (a class extending more than one classes) because it leads to ambiguity.

Conclusion

Inheritance is a powerful feature in Java, it helps to reduce code redundancy and makes your code modular. It's a crucial part of Java's OOP model. As you progress, you'll see how inheritance plays a vital role in other OOP concepts like polymorphism and abstraction.

Remember, practice is the key to mastering any concept, so try creating your own classes and experimenting with inheritance.

Happy Coding!