When we consider a Java program, it can be defined as a collection of objects that communicate via invoking each other's methods. Let us now briefly look into what do class, object, methods, and instance variables mean.

Object − Objects have states and behaviors. Example: A dog has states - color, name, breed as well as behavior such as wagging their tail, barking, eating. An object is an instance of a class.

Class − A class can be defined as a template/blueprint that describes the behavior/state that the object of its type supports.

Methods − A method is basically a behavior. A class can contain many methods. It is in methods where the logics are written, data is manipulated and all the actions are executed.

Instance Variables − Each object has its unique set of instance variables. An object's state is created by the values assigned to these instance variables.

First Java Program
Let us look at a simple code that will print the words Hello World.

Example

public class MyFirstJavaProgram {

/* This is my first java program.
* This will print 'Hello World' as the output
*/

public static void main(String []args) {
System.out.println("Hello World"); // prints Hello World
}
}

C:\> javac MyFirstJavaProgram.java
C:\> java MyFirstJavaProgram
Hello World

 This free site is ad-supported. Learn more
​