/**

* Day 7 - Memory Basics: Stack vs Heap

*

* Concept:

* Java uses two types of memory:

* 1. Stack - for primitives and method calls (fast, limited)

* 2. Heap - for objects (slower, large, automatic cleanup)

*

* This example demonstrates:

* - How primitives are stored on stack

* - How objects are stored on heap with references on stack

* - Difference between primitive and reference assignment

*

* Real-life analogy:

* Stack = Quick, organized checkout counter

* Heap = Slower, large storage warehouse

*/

public class StackVsHeapExample {

/**

* Main method - entry point of the program

*/

public static void main(String[] args) {

System.out.println("--- Primitives (Stack Storage) ---");

// Primitives stored on stack

int age = 25;

int salary = 100000;

System.out.println("Age: " + age);

System.out.println("Salary: " + salary);

// Modifying primitives

int temp = age;

age = salary;

salary = temp;

System.out.println("After swap:");

System.out.println("Age: " + age); // 100000

System.out.println("Salary: " + salary); // 25

// Key: Primitives are INDEPENDENT

System.out.println("\n--- Objects (Heap Storage) ---");

// Objects stored on heap, references on stack

Student s1 = new Student("Tejas", 20);

Student s2 = s1; // s2 gets same reference

System.out.println("s1: " + s1.name + ", Age: " + s1.age);

System.out.println("s2: " + s2.name + ", Age: " + s2.age);

// Modifying through s1

s1.name = "Raja";

System.out.println("\nAfter s1.name = 'Raja':");

System.out.println("s1: " + s1.name); // "Raja"

System.out.println("s2: " + s2.name); // "Raja" (same object)

// Key: Both references point to SAME object

System.out.println("\n--- Creating New Object ---");

// s2 now points to different object

s2 = new Student("Priya", 19);

System.out.println("s1: " + s1.name + ", Age: " + s1.age); // "Raja"

System.out.println("s2: " + s2.name + ", Age: " + s2.age); // "Priya"

// Now s1 and s2 point to DIFFERENT objects

System.out.println("\n--- Mixed Primitive and Reference ---");

demonstrateMemory();

}

/**

* Method to demonstrate stack and heap memory usage

*/

public static void demonstrateMemory() {

// Variables on stack

int price = 50000; // Primitive on stack

String carModel = "Tesla"; // Reference on stack, String on heap

Car car = new Car("Red"); // Reference on stack, Car object on heap

System.out.println("Inside method:");

System.out.println("Price: " + price);

System.out.println("Model: " + carModel);

System.out.println("Car color: " + car.color);

// After method ends:

// - All stack variables freed

// - Heap objects freed when no references exist

}

/**

* Inner class to represent Student

*/

static class Student {

String name;

int age;

Student(String name, int age) {

this.name = name;

this.age = age;

}

}

/**

* Inner class to represent Car

*/

static class Car {

String color;

Car(String color) {

this.color = color;

}

}

}