Simple Program of Java

 Simple Program of Java

In this page, we will learn how to write the hello java program. We can write a simple hello java
program easily.To create a simple java program, you need to create a class that contains main
method. Let's understand the requirement first.

Requirement for Hello Java Example

For executing any java program, you need to

Install the JDK if you don't have installed it, download the JDK and install it.
http://www.oracle.com/technetwork/java/javase/downloads/index.html

set path of the jdk/bin directory.
Right Click on Computer icon
-->Properties
-->Advanced system settings
-->Environment Variables
-->Click on PATH then Edit button
-->Paste the path of java
(For java Path go you C:\Program Files\Java\jdk1.*.*\bin
Right click on any program click go properties and copy the location or copy address bar)

create the java program
compile and run the java program

Creating hello java example

Let's create the hello java program:

    class Simple
          { 
             public static void main(String args[])
             { 
               System.out.println("Hello Java"); 
             } 
           } 

   save this file as Simple.java

To compile:    javac Simple.java
To execute:    java Simple

Output:Hello Java

Understanding first java program

 Let's see what is the meaning of class, public, static, void, main, String[], System.out.println().

class keyword is used to declare a class in java.

public keyword is an access modifier which represents visibility, it means it is visible to all.

static is a keyword, if we declare any method as static, it is known as static method.
The core advantage of static method is that there is no need to create object to invoke the static
method. The main method is executed by the JVM, so it doesn't require to create object to invoke
the main method. So it saves memory.

void is the return type of the method, it means it doesn't return any value.

main represents startup of the program.

String[] args is used for command line argument. We will learn it later.

System.out.println() is used print statement. We will learn about the internal working of
System.out.println statement later.