Ever felt like your objects needed to express themselves more? Enter: polymorphism in Java.

This week I finally got comfy with one of OOP’s most flexible (and misunderstood) concepts. Also, I’m building a Media Diary app for my uni assignment... 70% done and holding on to hope.

Let’s walk through the “why” and “how” of polymorphism with examples, real code, and the usual dose of developer humour.

What Is Polymorphism, Really?

In the world of object-oriented programming, polymorphism allows you to use a single interface to represent different underlying forms. In plain English? It’s the reason your code can treat different classes in the same way, as long as they share a common parent.

Let’s say you’ve got a few media types:

public class MediaEntry {
    public void displayInfo() {
        System.out.println("Generic media entry");
    }
}

public class BookEntry extends MediaEntry {
    public void displayInfo() {
        System.out.println("This is a book");
    }
}

public class GameEntry extends MediaEntry {
    public void displayInfo() {
        System.out.println("This is a game");
    }
}

Now, if you do this:

MediaEntry entry1 = new BookEntry();
MediaEntry entry2 = new GameEntry();

entry1.displayInfo(); // prints: This is a book
entry2.displayInfo(); // prints: This is a game

Boom. Polymorphism in action. One type, many behaviours.

Quick Uni Update: Media Diary in the Works

My OOP assignment at uni is now about 70% complete. Belief is what we have to hold on to, right? I’ve been building a full-featured Media Diary app using classes, objects, interfaces, and just the right amount of late-night debugging.

You might remember I mentioned the UML diagram a few blogs ago. Since then, I’ve been adding functionality like time tracking, media categorisation, and comparing user habits. It’s still a work in progress. The final post-mortem (I mean, blog post) will come when it’s finished. But for now: progress is being made.

Why Use Polymorphism?

Here’s why polymorphism is worth adding to your toolkit:

• You can write flexible and reusable code
• You reduce complexity by programming to interfaces
• You make your code easier to extend without rewriting the old stuff

It also keeps your methods neat. For example, if you’re looping through a bunch of MediaEntry objects, you don’t need to know if one’s a book or a game. Java will call the right method for each one. Magic.

Final Thoughts

Polymorphism isn’t just a technical term, it’s a vibe. It lets your objects be who they need to be, when they need to be. It’s like method acting, but with less drama and more curly braces.

I’m starting to really appreciate how these OOP principles click together. It’s like assembling IKEA furniture: confusing at first, then suddenly, everything fits.

Next up: abstraction, where Java starts revealing just enough to keep things interesting, like a magician who never shows all their cards.