Object-Oriented Java
Learn about object-oriented programming in Java. Explore syntax for defining classes and creating instances.
StartKey Concepts
Review core concepts you need to learn to master this subject
Java objects’ state and behavior
Java instance
Java dot notation
Constructor Method in Java
Creating a new Class instance in Java
Reference Data Types
Constructor Signatures
null Values
Java objects’ state and behavior
Java objects’ state and behavior
public class Person {
// state of an object
int age;
String name;
// behavior of an object
public void set_value() {
age = 20;
name = "Robin";
}
public void get_value() {
System.out.println("Age is " + age);
System.out.println("Name is " + name);
}
// main method
public static void main(String [] args) {
// creates a new Person object
Person p = new Person();
// changes state through behavior
p.set_value();
}
}
In Java, instances of a class are known as objects. Every object has state and behavior in the form of instance fields and methods respectively.
- 1All programs require one or more classes that act as a model for the world. For example, a program to track student test scores might have Student, Course, and Grade classes. Our real-world concer…
- 2The fundamental concept of object-oriented programming is the class. A class is the set of instructions that describe how an instance can behave and what information it contains. Java has pre-d…
- 3In order to create an object (an instance of a class), we need a constructor method. The constructor is defined within the class. Let’s take a look at the Car class with a constructor. The constr…
- 4Our last exercise ended with printing an instance of Store, which looked something like [email protected] The first part, Store, refers to the class, and the second part @6bc7c054 refers to the insta…
- 5To create objects with dynamic, individual states, we’ll use a combination of the constructor method and instance fields. In order to assign a value to an instance variable, we need to alter our …
- 6Now that our constructor has a parameter, we must pass values into the method call. These values are referred to as arguments; once they are passed in, they will be used to give the instance fiel…
- 7Objects are not limited to a single instance field. We can declare as many fields as are necessary for the requirements of our program. Let’s change Car instances so they have multiple fields. We…
- 8Java 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 def…
What you'll create
Portfolio projects that showcase your new skills
A Basic Calculator
It's time to build fluency in Object Oriented Java. In this next Pro Project, we're going to practice Classes, Methods, Objects in Java so you can hone your skills and feel confident taking them to the real world. Why? It's vital that you get comfortable creating classes and writing methods that perform various operations. What's next? Arithmetic operations, divisibility rules, Java methods. You got this!
Build A Droid
Practice object-oriented Java by creating a `Droid` class and creating different instances of Droid. Droids are robots built to perform tasks. A droid can be built for any task so it's the perfect candidate for a Java class!
How you'll master it
Stress-test your knowledge with quizzes that help commit syntax to memory