07 - Introduction to Object-Oriented Programming

Object-Oriented Programming (OOP) is the foundation of Java and Hytale modding. Instead of just having variables and methods floating around, we organize them into classes and objects.

What is a Class?

A class is a blueprint for creating objects. Think of it like a recipe or a template.

What is an Object?

An object is an instance created from a class. If a class is a blueprint, an object is the actual thing built from that blueprint.

Class vs Object

Class = Blueprint (the idea of a player) Object = Actual thing (Alice, Bob, specific players)

One class can create many objects, just like one recipe can make many cakes!

Creating a Simple Class

Let's create a Sword class for Hytale:

Using the class:

Constructors

Instead of setting properties one by one, use a constructor to initialize objects:

Now creating swords is easier:

Constructor Rules

Same name as the class
No return type (not even void)
Called automatically when you use new
Can have multiple constructors (overloading)

The `this` Keyword

this refers to the current object. Use it to clarify when parameter names match property names:

Without this, Java gets confused:

Practical Examples

Item Class

public class Main {
    public static void main(String[] args) {
        Item potion = new Item("Health Potion", "Consumable", 5, 0.5);
        
        potion.use();  // Used Health Potion. Remaining: 4
        System.out.println("Total weight: " + potion.getTotalWeight()); // 2.0
    }
}

Monster Class

Block Class

Access Modifiers (Preview)

You've seen public - it means "anyone can access this". We'll learn more about access control later, but here's a preview:

For now, use public for everything. We'll learn when to use private in the next article.

Why Use Classes?

Classes help you:

Organize related data and methods together
Reuse code easily (create many objects from one class)
Model real-world things (players, items, monsters)
Maintain code (changes in one place affect all objects)

Without classes, managing 100 players would require 100 separate variables for each property. With classes, it's just 100 Player objects!

Practice Exercises

Create a Potion Class:
- Properties: name, healAmount, uses
- Constructor to set all properties
- Method drink() that heals and decreases uses
- Method isEmpty() that returns true if uses less than or equal to 0
Create a Chest Class:
- Properties: isLocked, itemCount, capacity
- Constructor
- Method addItem() that checks capacity
- Method unlock() that sets isLocked to false
- Method isFull() that checks if itemCount >= capacity
Create a Villager Class:
- Properties: name, profession, tradeCount
- Constructor
- Method greet() that prints a greeting
- Method trade() that increases tradeCount
- Method getInfo() that displays all properties
Create Multiple Objects: Using any class you made, create 3 different objects and test all their methods.

07 - Introduction to Object-Oriented Programming

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