Java Hello World Program

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This presentation explains the 'Hello World' program in Java.

This presentation explains the 'Hello World' program in Java.

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  • 1. Java Hello World ProgramBy JavaWithUs ( www.javawithus.com )
  • 2. The ProgramFirst, let us look at the complete program :public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}The output will be :Hello World
  • 3. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}public is an access specifier which states thatthe class is accessible from any other class
  • 4. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}class defines a class or in simpler words – aprogram
  • 5. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}HelloWorld is the name of the class ( orprogram ). You can give any other nameBUT…
  • 6. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}… that name should follow the rules of identifiers :1. It should begin with a letter2. Lowercase letters, upper case letters andnumbers can be used. Only $ and _ specialcharacters are allowed.3. Keywords ( certain reserved words ) cannot beused as identifiers.4. Spaces are not allowed.
  • 7. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}The opening and closing braces specify thestarting and ending of the class.
  • 8. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}Within the class, we have a method.
  • 9. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}The method has a header or methoddeclaration ….
  • 10. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}… and a body
  • 11. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}The word public in the method header is thesame as the keyword public used for theclass. Here, it indicates that other classescan call this method.
  • 12. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}static specifies that we can invoke thismethod without creating an object of theclass.
  • 13. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}void indicates that the method does notreturn any value.
  • 14. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}main is the name of the method. For aprogram to be run, the name of the methodshould always be main.
  • 15. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}With the parentheses are the arguments.
  • 16. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}It takes a String array as an arguments andstores it in the variable args.
  • 17. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}A String is a group of letters. An array is agroup of Strings.
  • 18. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}The parameters to main method are passedthrough command line.
  • 19. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}This line prints the message to the screen.Anything within the quotes is displayed onthe screen.
  • 20. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Hello World” );}}System is a predefined class. out is amember of that class and println is amethod.
  • 21. public class HelloWorld {public static void main ( String[] args ) {System.out.println ( “Welcome to JavaWithUs.com” );}}The above modified program printsWelcome to JavaWithUs.com
  • 22. To understand the HelloWorld program in abetter way, read the following article :http://www.javawithus.com/tutorial/the-hello-world-programLearn Java through the tutorials on ourwebsite.http://www.javawithus.com/tutorial/
  • 23. Presentation bywww.javawithus.com