Java Classes and 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 has attributes, such as weight and color, and methods, 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 keyword class:

Create a class named "Main" with a variable x:

             
              
              
 public class Main {
   int  x = 5;
} 
              
            

Create an Object

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

To create an object of Main, specify the class name, followed by the object name, and use the keyword new:

Create an object called "myObj" and print the value of x:

             
              
              
  public class Main {
   int  x = 5;

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

Multiple Objects

You can create multiple objects of one class:

Create an object called "myObj" and print the value of x:

         
              
              
 public class Main {
   int  x = 5;

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