Classes

Classes are the building blocks of object-oriented programming (OOP) in Java. A class is a blueprint for creating objects, which are instances of the class. In this guide, we will cover the basics of Java classes.

Creating a Class

To create a class in Java, you use the class keyword followed by the name of the class. Here's an example:

public class Person {
    String name;
    int age;
}

In this example, we have created a class called Person. The class has two instance variables: name and age.

Instance Variables

Instance variables are variables that belong to each instance of a class. Each instance has its own copy of the instance variables. Here's an example:

Person person1 = new Person();
person1.name = "John";
person1.age = 25;

Person person2 = new Person();
person2.name = "Jane";
person2.age = 30;

In this example, we have created two instances of the Person class: person1 and person2. We have set the name and age instance variables for each instance.

Constructors

Constructors are used to create instances of a class. Here's an example of a constructor in the Person class:

public Person(String name, int age) {
    this.name = name;
    this.age = age;
}

In this example, we have defined a constructor that takes two parameters: name and age. The constructor initializes the name and age instance variables using the this keyword.

Using Constructors

Here's an example of how to use the Person constructor:

Person person1 = new Person("John", 25);
Person person2 = new Person("Jane", 30);

In this example, we have used the Person constructor to create two instances of the Person class: person1 and person2. We have passed in values for the name and age parameters.

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Last update: April 25, 2023
Created: April 25, 2023