JavaClasses and Objects

Java Classes/Objects

Java is an object-oriented programming language.

Everything in Java is associated with classes and objects, along with its attributes and methods. For example: in real life, a car is an object. The car hasattributes, such as weight and color, andmethods, such as drive and brake.

A Class is like an object constructor, or a "blueprint" for creating objects.

Create a Class

To create a class, use the keywordclass.

In this example, we create a class named "Main" with a variablex:

public class Main {  int x = 5;}

Create an Object

In Java, an object is created from a class. We have already created the class namedMain, so now we can use this to create objects.

To create an object ofMain, specify the class name, followed by the object name, and use the keywordnew:

public class Main {  int x = 5;  public static void main(String[] args) {    MainmyObj = new Main();    System.out.println(myObj.x);  }}

Multiple Objects

You can create multiple objects of one class:

public class Main {  int x = 5;  public static void main(String[] args) {    MainmyObj1 = new Main();  // Object 1    MainmyObj2 = new Main();  // Object 2    System.out.println(myObj1.x);    System.out.println(myObj2.x);  }}

Using Multiple Classes

You can also create an object of a class and access it in another class. This is often used for better organization of classes (one class has all the attributes and methods, while the other class holds themain() method (code to be executed)).

Remember that the name of the java file should match the class name. In this example, we have created two files in the same directory/folder:

• Main.java
• Second.java

public class Main {  int x = 5;}

class Second {  public static void main(String[] args) {    MainmyObj = new Main();    System.out.println(myObj.x);  }}

When both files have been compiled:

Run the Second.java file:

And the output will be: