Java Naming Conventions and First Program

First code

Let us begin to write the most basic code to exist in any coding language; that is the “ Hello World” program.

From here we begin to understand the coding structure of java language. for that, Let us have a look here.

first program in java

Code in Java

Run

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

Output

Hello World

Remember guys, Java is a case sensitive language.

Here we are writing a program to print Hello World on the output screen.

  • The class is named as Main.  The outer class can only be either public or default. We make a class public so that it is accessible from outside ( by a JVM ).
  • If there is a dot ( . ) after a class name, it indicates that We are accessing one of its static members.

Here if we look at the statement  System.out.println(“Hello world”);

  • System is a class.
  • System.out indicates that we are accessing ‘ out ‘ which is a static reference variable/ pointer which represents an object.
  • ‘ println ‘ is a member function of the object ‘ out ‘.[ ‘ println ‘ prints the output in a new line automatically while ‘ print ‘ prints the output in the same line. ]

Now if we look at the statement public static void main(String[] args)

  • Here public is an access specifier that allows the main method to be accessible everywhere.
  • Static helps the main method to get loaded without getting called by any instance/object.
  • Void clarifies that the main method will not return any value.
  • Main is the name of the method.
  • String[] args: Here we are defining a String array to pass arguments at command line. args is the variable name of the String array. It can be changed to anything such as String [] a.

Class and Interfaces:

  • Class names are nouns, in which the first letter of each internal word is capital. This type of representation is also known as the camel case.
  • The use of whole words is preferred rather than abbreviations and acronyms ( except in the case where the abbreviation is more widely used than the actual word ).
  • The interface names should also be capitalized just like done in classes. 

Packages:

  • The prefix of a unique package name is always written in all-lowercase ASCII letters and should be one of the top-level domain names, currently com, edu, gov, mil, net, org.
  • If the name contains multiple words, it should be separated by dots (.) such as java.util, java.lang.
  • Subsequent components of the package name vary according to an organization’s own internal naming conventions.

Variables:

  • Variables: Variable names should be short yet meaningful.
  • It starts with a lowercase letter. The usage of One- character variable should be avoided. Although permitted, initializing variable names with either underscore(‘_’) or dollar sign ‘$’ characters should not be done.

Method:

  • Methods should be verbs, in mixed case with the first letter lowercase, and with the first letter of each internal word capitalized.

 

Constant Variables:

  • The constant variables should all be in upper case with the words separated with the help of an underscore ‘ _ ‘.
  • It may contain digits but not as the first letter.