Variables

Relax. We'll talk through this in plain words — no textbook voice.

A variable is a named storage spot used to hold data. Java is a statically typed language, so you have to declare a variable's data type before you use it. Think of it as Java asking you upfront, "what type are we putting in this box?"

java

public class Main {
  public static void main(String[] args) {
    String name = "Aung";
    int age = 30;
    double height = 5.8;
    boolean isStudent = false;

    System.out.println("Name: " + name);
    System.out.println("Age: " + age);
    System.out.println("Height: " + height);
    System.out.println("Student: " + isStudent);
  }
}

String stores text. int stores whole numbers, double stores decimal numbers, and boolean stores true/false values. The + operator, when used with a String, joins pieces of text together.

You should see

Name: Aung Age: 30 Height: 5.8 Student: false

Real-world use

All app data—user profiles, product prices, login status, scores, inventory counts—starts out being managed with this same variable concept.

Easy traps

Writing int age = "30"; is a type mismatch error, because it stores 30 as text instead of a number.