Java Introduction

• Java is platform independent programming language.
• Java creates a bytecode that can be run on any type of machine with the help of Java Virtual Machine (JVM).
• Java is secure language because java is not using pointers.
• Java is also called "write once and run anywhere" programming language.

First Java Program

• Java program can be written in Notepad or any text editor.
• Java program starts by creating a class.

Example

class FirstJavaProg {
	public static void main (String args[])
	{
		System.out.println ("Hello ! Dear learner");
	}
}

Output of the program

Hello ! Dear learner

Explanation of the program

• A class named FirstJavaProg is created.
• A java program starts from main() method. Hence, main() method is created in the class.
• Main() method must be defined as public static void and must receives array of arguments of String type .
• To display a message, the statement System.out.println() is used.
• Class and main() method are properly closed by curly brackets.

Compiling Java Program

• Java program is complied using the command.

  		javac FirstJavaProg.java
  

• If command 'javac' is not working, then set 'path' environment variable to java directory.

  Example

  		set path = C:\Program Files\Java\jdk1.8.0_102\bin
  

Running Java Program

• Java program is run by using the command 'java'. Remember do not include .java extension.

  		java FirstJavaProg
  

  
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