Instance methods in Java - Mini Project: Build & Apply

Instance Methods in Java

📖 Scenario: You are creating a simple program to manage a car's details and actions. You will use instance methods to show how each car object can perform actions on its own data.

🎯 Goal: Build a Java class called Car with instance variables and instance methods. Then create an object of this class and call its methods to display information and perform actions.

📋 What You'll Learn

Create a class named Car with instance variables make and year.

Add an instance method displayInfo that prints the car's make and year.

Add an instance method startEngine that prints "Engine started".

Create a Car object in the main method and call both instance methods.

💡 Why This Matters

🌍 Real World

Instance methods let objects perform actions using their own data, just like a real car can start its own engine or show its own details.

💼 Career

Understanding instance methods is essential for object-oriented programming, which is widely used in software development jobs to model real-world entities.

1

Create the Car class with instance variables

Create a class called Car with two instance variables: String make and int year.

Java

public class Car {
    // Your code here
}

Need a hint?

Instance variables are declared inside the class but outside any method.

2

Add instance methods to the Car class

Inside the Car class, add an instance method displayInfo that prints the car's make and year, and another instance method startEngine that prints "Engine started".

Java

public class Car {
    String make;
    int year;

    // Your code here
}

Need a hint?

Instance methods use instance variables to perform actions related to the object.

3

Create a Car object and set its variables

In a Main class with a main method, create a Car object named myCar. Set myCar.make to "Toyota" and myCar.year to 2020.

Java

class Car {
    String make;
    int year;

    void displayInfo() {
        System.out.println("Make: " + make + ", Year: " + year);
    }

    void startEngine() {
        System.out.println("Engine started");
    }
}

public class Main {
    public static void main(String[] args) {
        // Your code here
    }
}

Need a hint?

Use the new keyword to create an object and dot notation to set variables.

4

Call instance methods and print output

In the main method, call myCar.displayInfo() and myCar.startEngine() to print the car's details and start the engine.

Java

class Car {
    String make;
    int year;

    void displayInfo() {
        System.out.println("Make: " + make + ", Year: " + year);
    }

    void startEngine() {
        System.out.println("Engine started");
    }
}

public class Main {
    public static void main(String[] args) {
        Car myCar = new Car();
        myCar.make = "Toyota";
        myCar.year = 2020;

        // Your code here
    }
}

Need a hint?

Call instance methods using the object name followed by dot and method name with parentheses.