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

• All code is contained within a class.
• The file name must match the class name
• The file name have a .java extension
• All statements are contained within a method,
• in this case named main().
• All other statements are terminated with a semi-colon (;).
• Java language is case-sensitive!
• HelloWorld is not the same as helloworld,
  
• String is not the same as string.