Learn
Java: Introduction to Classes
Classes: Review

Java is an object-oriented programming language where every program has at least one class. Programs are often built from many classes and objects, which are the instances of a class.

Classes define the state and behavior of their instances. Behavior comes from methods defined in the class. State comes from instance fields declared inside the class.

Classes are modeled on the real-world things we want to represent in our program. Later we will explore how a program can be made from multiple classes. For now, our programs are a single class.

public class Dog { // instance field String breed; // constructor method public Dog(String dogBreed) { /* value of parameter dogBreed assigned to instance field breed */ breed = dogBreed; } public static void main(String[] args) { /* create instance: use 'new' operator and invoke constructor */ Dog fido = new Dog("poodle"); /* fields are accessed using: the instance name, `.` operator, and the field name. */ fido.breed; // "poodle" } }

Instructions

The text editor contains a Dog class. Play around with the code!

Try to add and remove instance fields. Create instances with different values. Access and print different fields.

Folder Icon

Take this course for free

Already have an account?