Classes and Objects 🚀

Mentor's Note: In Java, you can't just write a line of code in the middle of nowhere. Everything must live inside a Class. It’s the "Home" for your code! 💡

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🌟 The Scenario: The Smartphone Factory 🏭

Imagine you own a factory that makes smartphones.

• The Class (The Blueprint): Before making any phone, engineers create a detailed design 📝. This design says every phone must have a color, a storage size, and a power button. 📦
• The Object (The actual Phone): Using that blueprint, the factory produces an actual iPhone 📱. One is Space Grey (Object 1), another is Gold (Object 2).
• The Result: You can't make a call using the blueprint; you need the actual object! ✅

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📖 Concept Explanation

1. What is a Class?

A class is a template or blueprint that describes the behavior/state that the object of its type supports.

2. What is an Object?

An object is an instance of a class. It has state (variables) and behavior (methods).

3. The new Keyword 🏗️

The new keyword is the "Start Button" of your factory. It tells Java to allocate memory and create a real object from your class blueprint.

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🎨 Visual Logic: Blueprint to Reality

graph TD
    subgraph Blueprint: ["Class: Smartphone 📝"]
    A[Variable: Color]
    B[Method: call()]
    end
    Blueprint -- "new keyword" --> O1["Object: My iPhone 📱 (Space Grey)"]
    Blueprint -- "new keyword" --> O2["Object: Your Galaxy 📱 (Gold)"]

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💻 Implementation: The Factory Lab

Java (JDK 17+)

// 🛒 Scenario: Building a Phone
// 🚀 Action: Creating a class and object

class Smartphone {
    String model = "Pro Max"; // 📦 Attribute (State)

    void ring() { // ⚙️ Method (Behavior)
        System.out.println("Beep! Beep! 🔔");
    }
}

public class Main {
    public static void main(String[] args) {
        // 🏗️ Step 1: Instantiate the Object
        Smartphone myPhone = new Smartphone();

        // 🏷️ Step 2: Access properties
        System.out.println("Model: " + myPhone.model);

        // 📞 Step 3: Call methods
        myPhone.ring();
    }
}

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📊 Sample Dry Run

Step	Instruction	Memory State	Result
1	Smartphone myPhone	null	Reference created 📥
2	= new Smartphone();	Memory@101	Object born! 🏗️
3	myPhone.ring();	Running method	Output: Beep! 📤

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📈 Technical Analysis

• Class: Logical entity. No memory is allocated when a class is defined.
• Object: Physical entity. Memory is allocated as soon as the new keyword is used. 💾

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🎯 Practice Lab 🧪

Task: The Car Garage

Task: Create a class Car with attributes color and speed. Create two different car objects (one "Red", one "Blue") and print their details. Hint: Use the new keyword twice! 💡

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💡 Pro Tip: "Classes are the skeleton, Objects are the body. You need the skeleton to build the body!" - Vishnu Damwala

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