Variables Need Types 📦

A variable is a labeled box that stores a value. Java is extra careful: every box also says what kind of thing goes inside. That's its type.

public class Main {
    public static void main(String[] args) {
        String robotName = "RoverBot";
        int battery = 87;
        double speed = 1.5;
        boolean isCharging = false;

        System.out.println(robotName + " battery: " + battery + "%");
        System.out.println("Charging? " + isCharging);
    }
}

The pattern is always: type name = value;

Why types? 🤔

Types stop silly mistakes. If you try to put text into a number box, Java refuses before your robot ever moves:

int battery = "full"; // ❌ text can't go in an int box

That's a good thing! It's much better to find the bug at your desk than in the middle of a robot competition.

Naming boxes

Java programmers use camelCase: start lowercase, then a capital for each new word: batteryLevel, isCharging, tallestMountain.

🌡️ Fun fact

Weather stations measure temperature as decimals, like 21.5 degrees, so a program storing them would use double. The number of days in a week? Always whole, so int is perfect.