Simple Program of Java

By : Mungara Chirantan

In this page we will learn How to Start A first Java program and how we can Run it . ok so lets Start

To create a simple java program, you need to create a class that contains main method. Let's understand the requirement first.

Requirement for Java Program Development 

• install the JDK if you don't have installed it, download the JDK and install it.
• set path of the jdk/bin directory.
• create the java program
• compile and run the java program

Creating hello java example

 Class XYZ

{

    public Static void main(String args[]);

 {

      System.out.println("Hello Gays How are U");

} }

Note :

1. save this file as a class name like XYZ.java.
2. compile : javac xyz.java
3. execute  : java xyz.java

Understanding first java program

• 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.

Valid java main method signature

1. public static void main(String[] args)  
2. public static void main(String []args)  
3. public static void main(String args[])  
4. public static void main(String... args)  
5. static public void main(String[] args)  
6. public static final void main(String[] args)  
7. final public static void main(String[] args)  
8. final strictfp public static void main(String[] args) 

 Invalid java main method signature

 

1. public void main(String[] args)  
2. static void main(String[] args)  
3. public void static main(String[] args)  
4. abstract public static void main(String[] args)