First Java Program

Now we will learn how to write the first java program. We can write a simple Hello World java program easily but first need to understand of required Software for java program

Requirements for java Program

For executing any java program we need given things.

• Download JDK and Install if you don't have installed it.
• Set path of the jdk/bin directory.
  • Go to MyComputer properties -> advanced tab -> environment variables -> new tab of user variable -> write variable name PATH-> write java path of bin folder in variable value -> OK
• Create the java program
• Compile and execute java program

Public Static Void Main

You will see it in almost every Java program. You know, the declaration public static void main. It is the means by which you create a main method within the Java application. JVM will always look for a specific method signature to start running an application, and that would be public static void main(String args[]).

• class keyword is used to declare a class in java. . The entire class definition, including all of its members, will be between the opening curly brace { and the closing curly brace }
• public keyword is an access modifier which represents visibility. Public means that this Method will be accessible by any Class
• static is a keyword. It means the given Method or variable is not instance-related but Class related. The main method is executed by the JVM, so it doesn't require to create an object to invoke the main method.
• void . It is used to define the Return Type of the Method. void is the return type of the method. It means it doesn't return any value.
• main is the name of the Method. This Method name is searched by JVM for starting point of the program.
• String[] args is used for command line argument.

System.out.println("Test");

System is a predefined class that provides access to the system, and out is the variable of type output stream that is connected to the console. Output is actually accomplished by the built-in println( ) method.

Comments

The comments are the statements that are not executed by the compiler and interpreter. The comments can be used to provide information or explanation about the variable, method, class or any statement. They can either be multi-line or single line comments. A multi-line comment must begin with /* and end with */. For single line you may directly use //.