📦 All About Java Memory

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Hello! I’m Java’s Memory Space! 👋

I’m here to store everything you create: variables, objects, methods… all of it!
But guess what?
I have TWO special zones inside me:

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📄 Stack Memory

• Quick and small storage.
• Used for:
  • Local variables
  • Method calls
  • References to objects
• Super fast, but gets cleared when the method ends!

🧠 Think of it like your desk — only the stuff you’re actively working on.

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📦 Heap Memory

• Big, long-term storage.
• Used for:
  • Objects (new Dog(), new Car())
  • Class instances
• Slower, but data stays until you don’t need it anymore!

🏡 Think of it like your closet — you store things you’ll use later.

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✨ Fun Code Example:

public class MemoryFun {
  public static void main(String[] args) {
    int num = 5;
    Dog myDog = new Dog();
  }
}

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🧠 Memory Map:

Stack:

Variable	Value
num	5
myDog	👉 (points to Dog in Heap)

Heap:

Object	Details
Dog	Dog object created by new Dog()

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1️⃣ Java Variables — What Are They?

🧠 Think of variables as little labeled boxes.

int age = 25;
String name = "Charlie";

[STACK] 📄
-------------
| age = 25          |
| name (ref)     | ---> [HEAP] 📦
                                     -------------
                                     | "Charlie"   |
                                     -------------

🛒 Variables = Labels
🧺 Objects/Strings = Things Stored

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📚 Why 25 is in Stack, but "Charlie" is in Heap?

1. int is a primitive type (like int, boolean, char, float, etc.)
2. Primitive types in Java are stored directly inside the Stack.
3. So age holds the actual value 25 right there in the Stack.

1. int age = 25;

✅ No pointer, no object — just the number 25!

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2. String name = "Charlie";

• String is a class (not a primitive type) — it’s an object!
• Java objects are always created/stored in the Heap.
• In the Stack, name only stores a reference (a tiny pointer 🔗) to the "Charlie" String object sitting in the Heap.

✅ Stack holds a link → Heap holds the actual data "Charlie".

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🧠 So in short:

Type	Where?	Why?
Primitive (int, char, etc.)	Stack 📄	Stored directly, tiny and fast
Objects (String, Dog, Car, etc.)	Heap 📦	Bigger, needs long-term space

⚡ Quick Extra Tip:

Even though "Charlie" is in Heap, if you wrote:

String greeting = "Hello";

Java might optimize it and store it in a special part of Heap called the String Pool to save memory — but still, it’s Heap, not Stack.

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🧠 Simple Rule:

If it’s a primitive → Stack
If it’s an object → Heap