Java Variables

🧠 Definition

A variable in Java is a container that holds data during the execution of a program. Each variable has a data type, which defines the kind of data it can store (e.g., integer, string).

Variables are the named memory locations used to store values for processing.

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✍️ Syntax

dataType variableName = value;

Example:

int age = 25;
String name = "Alice";
boolean isJavaFun = true;

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🌐 Real-World Analogy

Think of a variable like a labeled jar — if you put "sugar" in a jar labeled "SweetStuff", you can refer to it easily later.

| Label (variableName) | Contents (value) | Type of Contents (dataType) |
|----------------------|------------------|------------------------------|
| age                  | 25               | int                          |
| name                 | "Alice"          | String                       |
| isJavaFun            | true             | boolean                      |

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🧒 Explain Like I'm Five

"Imagine you have a toy box labeled ‘Lego’. If you want to play, you look at the box name to know what's inside. Java does something similar with variables!"

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🎯 Types of Variables in Java

Type	Scope	Default Value
Local	Declared inside a method	No default
Instance	Belongs to an object	Depends
Static	Belongs to a class (not instances)	Depends

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🔁 Example with Different Variables

public class VariableDemo {
  int instanceVar = 10;          // Instance variable
  static int staticVar = 20;     // Static variable

  void method() {
    int localVar = 5;            // Local variable
    System.out.println(localVar);
  }

  public static void main(String[] args) {
    VariableDemo obj = new VariableDemo();
    obj.method();
    System.out.println(obj.instanceVar);
    System.out.println(staticVar);
  }
}

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✅ Exercise

1. Declare three variables: int score, String playerName, boolean isAlive. Assign them values and print them.
2. Create a class with one static and one instance variable. Access both in main().

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🎉 Fun Fact

Did you know? Java is a statically typed language, which means you have to declare the type of a variable before using it. Unlike Python, where you can just do x = 5, in Java you must write int x = 5;.

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📌 Quick Recap

• Variables store data
• Must be declared with a type
• Can be local, instance, or static
• Are essential building blocks in any Java program