Classes and Objects
In this tutorial, you’ll learn about the building blocks of Java programming: classes and objects.
What are Classes and Objects?
A class is a blueprint for objects. It defines a datatype by bundling data and methods that work on the data into one single unit. An object is an instance of a class.
Defining a Class
To define a class, use the class
keyword:
public class Car {
// fields
String color;
String model;
// methods
void drive() {
System.out.println("Driving the car");
}
}
Creating an Object
To create an object, use the new
keyword:
public class Main {
public static void main(String[] args) {
Car myCar = new Car();
myCar.color = "Red";
myCar.model = "Toyota";
myCar.drive();
}
}
In the example above, myCar
is an object of the class Car
.
Constructors
A constructor is a special method that is called when an object is instantiated. It can be used to set initial values for object attributes:
public class Car {
String color;
String model;
// Constructor
public Car(String color, String model) {
this.color = color;
this.model = model;
}
}
Access Modifiers
Access modifiers specify the accessibility of a class, method, or field. The four access modifiers in Java are:
public
– accessible from anywhereprotected
– accessible within the same package and subclassesdefault
– accessible only within the same packageprivate
– accessible only within the same class
Continue exploring our intermediate tutorials to learn more about Java programming.