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Java Concepts I’m Mastering – Part 9: Inheritance in Java (extends Keyword)

Continuing my journey of mastering Java fundamentals.

Today’s focus: Inheritance — the mechanism that allows one class to acquire properties and behavior of another class.

What is Inheritance?

Inheritance means:

A child class can reuse the fields and methods of a parent class.

This promotes:

Code reusability

Clean hierarchy

Logical relationships

Syntax

class ChildClass extends ParentClass {
    // additional features
}

Example

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

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

Now:

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

The Dog class reuses behavior from Animal.

Types of Inheritance in Java

Single

Multilevel

Hierarchical

(Java does not support multiple inheritance with classes — but it does through interfaces.)

Why It Matters

Inheritance helps in:

Building scalable systems

Reducing code duplication

Implementing runtime polymorphism

It works closely with method overriding, which I covered earlier in this series.

What I Learned

Use inheritance for “is-a” relationships

Avoid unnecessary deep hierarchies

Combine with abstraction for clean design

Inheritance is a core building block of object-oriented design.

Next in the series: Final Keyword in Java (final variable, method, class)