Java Data Types 🚀

Mentor's Note: Java is a "Statically Typed" language. This means you must tell Java exactly what kind of item you are putting in a box, and you can't change your mind later! 💡

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🌟 The Scenario: The Labeled Warehouse 📦

Imagine you are a warehouse manager.

• The Logic:
  • You have Small Boxes for single numbers (byte). 🔢
  • Large Boxes for massive numbers (long). 🔢
  • Padded Boxes for fragile decimals (double). 💲
  • Check-mark Boxes for Yes/No (boolean). ✅
• The Result: By using the right size box, you save space and prevent "items" from breaking. In Java, this is why we have 8 Primitive Types. ✅

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📖 Concept Explanation

1. Primitive Data Types (Simple)

These are built-in and have a fixed size.

Type	Size	Range / Purpose
int	4 bytes	Whole numbers (-2.1B to 2.1B)
double	8 bytes	Decimals (Most precise)
char	2 bytes	Single letter (e.g., 'A')
boolean	1 bit	true or false

2. Reference Data Types (Complex)

These point to "Objects." They can hold complex data and have their own methods. - Examples: String, Arrays, Classes. - Default Value: Primitives default to 0/false; Reference types default to null. 🚫

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🎨 Visual Logic: The Storage Map

graph TD
    A[Java Data Types] --> B[Primitive]
    A --> C[Reference]
    B --> B1[Numeric: int, long, double]
    B --> B2[Logical: boolean]
    B --> B3[Character: char]
    C --> C1[String 🚂]
    C --> C2[Arrays 📦]
    C --> C3[Objects 👤]

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💻 Implementation: The Type Lab

Java (JDK 17+)

// 🛒 Scenario: Storing a Student Record
// 🚀 Action: Using different data types

public class Main {
    public static void main(String[] args) {
        // 📦 Labeled Boxes
        int rollNo = 101;
        double percentage = 95.5;
        char grade = 'A';
        boolean isPassed = true;
        String name = "Vishnu"; // Reference Type 🚂

        System.out.println(name + " (Roll: " + rollNo + ") Grade: " + grade);
    }
}
// 🛍️ Outcome: "Vishnu (Roll: 101) Grade: A"

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📊 Sample Dry Run

Step	Instruction	Variable	Memory Size	Value
1	int x = 5;	x	4 Bytes	5 📦
2	double y = 5.5;	y	8 Bytes	5.5 📦
3	String s = "Hi";	s	Pointer	"Hi" (in Pool) 🏊

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📉 Technical Analysis

• Precision: Always prefer double over float for financial data to avoid rounding errors. 💰
• The String Pool: Java doesn't create a new String object if you use the same text twice—it reuses the existing one to save memory! 🧠

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🎯 Practice Lab 🧪

Task: The Price Tag

Task: Create variables for a product_price (decimal), quantity (whole number), and currency_symbol (character). Print them together. Hint: double, int, and char. 💡

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💡 Pro Tip: "Type is a character, but data is its personality." - Anonymous

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