Classes & Objects

You've learned about variables, methods, and control flow. Now it's time to put them all together. Classes are blueprints that let you create your own custom "data types", and objects are instances of those classes.

What is a Class?

A class is like a blueprint or template. It defines what data (variables) and actions (methods) something should have, but it doesn't create the actual thing yet.

public class Robot {
    // Variables (what the robot has)
    private DcMotor leftMotor;
    private DcMotor rightMotor;
    private boolean isMoving;
    
    // Methods (what the robot can do)
    public void moveForward() {
        leftMotor.setPower(0.5);
        rightMotor.setPower(0.5);
        isMoving = true;
    }
    
    public void stop() {
        leftMotor.setPower(0);
        rightMotor.setPower(0);
        isMoving = false;
    }
}

What is an Object?

An object is an instance of a class.

// Create objects from the Robot class
Robot myRobot = new Robot();      // This creates one robot

Constructors

A constructor is a special method that runs when you create a new object. It sets up the initial state:

public class Hardware {
    private DcMotorEx motor1;
    
    // Constructor - runs when you create a new Hardware
    public GameTimer(hardwareMap hw) {
        motor1 = hw.get(DcMotorEx.class,"m1");
    }
}

// Using the constructor
Hardware hardwareClass = new Hardware(hardwareMap);

Quick Reference

Concept	What It Is	Example
Class	Blueprint/template	public class Robot { ... }
Object	Instance of a class	Robot myRobot = new Robot();
Constructor	Setup method for new objects	public Robot(String name) { ... }