Inheritance in Java

Inheritance lets a child (sub) class acquire the fields and methods of a parent (super) class using extends. It models an IS-A relationship and promotes code reuse.

Java

class Animal {
    void eat() { System.out.println("Eating..."); }
}
class Dog extends Animal {
    void bark() { System.out.println("Barking..."); }
}

Dog d = new Dog();
d.eat();   // inherited
d.bark();

Eating... Barking...

Types of Inheritance

Types of inheritance (arrows point from child to parent)

Type	Structure	Supported with classes?
Single	A → B	Yes
Multilevel	A → B → C	Yes
Hierarchical	A → B, A → C	Yes
Multiple	A, B → C	No (only through interfaces)

Why no multiple inheritance?If two parents had the same method, the child wouldn't know which to use (the diamond problem). Java avoids this ambiguity for classes.

The super Keyword

Java

class Vehicle { Vehicle() { System.out.println("Vehicle created"); } }
class Bike extends Vehicle {
    Bike() {
        super();   // calls parent constructor (implicit anyway)
        System.out.println("Bike created");
    }
}
new Bike();

Vehicle created Bike created

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