Everything is class in java.
  • If you are using some tool like Eclipse or Net Bean; your application will be layered within a project/package, and irrespective of tools, there would be a main controller or entry point in your code.
  • How it is architected?
    • Class
      • fields to all methods in the class
      • public constructor
      • methods or function
        • public static void or return main (arguments ) condition like throws IOException
          OR
        • public static void or return main (arguments ) condition like throws
          • fields to the local method.
declaration a class
  • ["public"] ["abstract"|"final"]"class" class_name ["extends" object_name]
    "{"
    // properties declarations
    // behavior declarations
    }
field declaration
  • Scope of the field : [ "public" | "private" | "protected" ] [ "final" ] [ "static" | "transient" | "volatile" ]
  • data type : int, Sting, double , long , float
  • declaration only : scope data_type field_name
  • initialization of declared field field_name = value;
  • declaration and initialization : data_type var_name = value ;
  • By convention, the first letter should be capitalized.
  • This type of naming convention is known as Pascal naming convention or Upper Camel Case. According to the lower camel naming convention, initial letter is in small cap.
  • Method and field names use the lower camel naming convention.
    		•
     
    Command Line code

    import java io.*;
    //javac simple.java
    public class simple
    {
    public static void main(String args[])
    {
    System.out.println("Hell World");
    }
    }
    Using GUI- Swing

    import javax.swing.*;
    public class test {
    public static void main(String[] args) {
    String str = "Hello Wrold";
    JOptionPane.showMessageDialog(null, str) ;
    }
    }