Extending classes (extends)

The extends keyword is used to create a subclass that inherits from a superclass.

Syntax:

class Subclass extends Superclass {
    // additional fields and methods
}

Example:

class Animal {
    String name;
    void eat() {
        System.out.println(name + " is eating");
    }
}

class Dog extends Animal {
    void bark() {
        System.out.println(name + " is barking");
    }
}

Usage:

Dog dog = new Dog();
dog.name = "Rex";
dog.eat();  // inherited from Animal
dog.bark(); // defined in Dog

What is inherited?

• All public and protected members (fields and methods)
• default (package‑private) members if subclass is in same package
• Private members are NOT inherited (but can be accessed indirectly via public/protected methods).

Java supports single inheritance: a class can extend only one direct superclass. Multiple inheritance of classes is not allowed, but multiple interface implementation is possible.

Inheritance hierarchy:

class Vehicle { }
class Car extends Vehicle { }
class ElectricCar extends Car { }