🔢 Working with Java Data Types

Master the foundation of Java programming through comprehensive examples and visual learning

🎯 Learning Objectives

By the end of this lesson, you will:

Master primitive and reference data types with real-world applications
Understand memory allocation and type conversion mechanisms
Apply wrapper classes and autoboxing in practical scenarios
Visualize data flow and memory management concepts

📊 Java Data Type Architecture

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Java Type System Overview

Java has a two-tier type system: Primitives (stored directly in memory) and Reference Types (stored as object references in heap memory).

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Memory Layout Visualization

Stack Memory               |    Heap Memory
---------------------------|---------------------------
int age = 25;             |    String name = "John";
double salary = 50000.0;  |    ┌─────────────────┐
boolean isActive = true;   |    │ String Object   │
                          |    │ value: "John"   │
Reference Variables:       |    └─────────────────┘
String name ────────────────────→ Heap Reference

🔢 Primitive Data Types Deep Dive

Numeric Types with Practical Examples

Type	Size (bits)	Range	Default Value	Real-World Use Case
`byte`	8	-128 to 127	0	Image pixel values, small counters
`short`	16	-32,768 to 32,767	0	Audio samples, temperature readings
`int`	32	-2,147,483,648 to 2,147,483,647	0	User IDs, counts, array indices
`long`	64	-9,223,372,036,854,775,808 to 9,223,372,036,854,775,807	0L	Timestamps, large file sizes, population counts
`float`	32	IEEE 754 (±3.4 × 10³⁸)	0.0f	Graphics coordinates, scientific calculations
`double`	64	IEEE 754 (±1.7 × 10³⁰⁸)	0.0d	Financial calculations, GPS coordinates

🎨 Practical Scenario: Building a Student Management System

// Real-world application of different data types
public class Student {
    // Using appropriate data types for different purposes
    private byte semester;           // 1-8 (fits in byte range)
    private short courseCount;       // Number of courses (0-500)
    private int studentId;          // Unique identifier
    private long phoneNumber;       // Phone numbers (large numbers)
    private float gpa;              // Grade Point Average (precision adequate)
    private double tuitionFee;      // Financial data (high precision needed)
    private boolean isActive;       // Status flag
    private char grade;             // Single character grade (A-F)
    
    // Constructor demonstrating type usage
    public Student(int id, String name, byte semester) {
        this.studentId = id;
        this.semester = semester;
        this.isActive = true;
        this.courseCount = 0;
        this.gpa = 0.0f;
        this.tuitionFee = 25000.50;  // Default tuition
        this.phoneNumber = 1234567890L;  // Note the 'L' suffix
    }
    
    // Method showing type conversions
    public void updateGPA(double newGPA) {
        // Explicit cast from double to float
        this.gpa = (float) newGPA;
        
        // Determine letter grade based on GPA
        if (newGPA >= 3.7) this.grade = 'A';
        else if (newGPA >= 3.0) this.grade = 'B';
        else if (newGPA >= 2.0) this.grade = 'C';
        else this.grade = 'F';
    }
}