How to write a Hello World application in Java?

Question

I have been trying to make the Hello World Java application. But when I try to run the program it says that my selection has no main type. Here is my source code.

public class HelloWorldClass {

    System.out.println("Hello world!");
}

What does your book or tutorial say about it being necessary to have a `public static main` method? — AntonH, May 10 '14 at 18:51

Afzaal Ahmad Zeeshan · Answer 1 · 2014-05-10T19:21:33.920

3

Because it has no main() method where the code would take the starting point. Use this

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

Please note there are some of the things you should always take a note of while programming. Which is also known as the syntax of the language.

Java requires you to have the class written as the FileName, HelloWorldClass is the name of the file of yours.

Then, any data type of it. In my case it is void which means it won't return anything to you in the end.

Also, you should write String[] args which is the Parameter to the method. I was last night trying to understand why I should write these? There is a method, which runs without these, but Java recommends you to add the parameters.

edited May 10 '14 at 19:21

answered May 10 '14 at 18:52

Afzaal Ahmad Zeeshan

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4

main method cannot be instantated..What does that mean? IMO we instantiate class only not methods. – Hello World May 10 '14 at 18:59
:Also how will you run main method without String[]args ?? – Hello World May 10 '14 at 19:01
@P.K普 It is just required to remove the ambiguity while running the main function. So, it removes any changes of adding a `new main()` :) I think you get it, if don't http://stackoverflow.com/questions/146576/why-is-the-java-main-method-static...Without that, the compiler would give the error, of writing the main method as`public static void main(String[] args) {...` I tried is last night hehehe :) – Afzaal Ahmad Zeeshan May 10 '14 at 19:02
I never thought about it thanks for this part. – Hello World May 10 '14 at 19:09
You cannot instantiate a method... you can however invoke it. – Ryman Holmes May 10 '14 at 19:10
@RymanHolmes, so that caused a downvote? :) Right? – Afzaal Ahmad Zeeshan May 10 '14 at 21:22
@AfzaalAhmadZeeshan Nope... I didn't downvote, You're answer was correct – Ryman Holmes May 11 '14 at 00:16

score 2 · Answer 2 · answered May 10 '14 at 18:53

2

When running Java you need a main method so the compiler knows what to run:

public class HelloWorldClass {

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

}

answered May 10 '14 at 18:53

user3574492

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How to write a Hello World application in Java?

2 Answers2