SESSION 6 Part4 Source File Structure - <Let's create a game!> Introduction of programming for absolute beginners

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SESSION 6 Part4

Source File Structure

Okay,
now that the ritual is complete,
let's take a basic look at the
structure of the source file.

Okay!

Yes please!

Comment

Your first program code（KotoTest's KNMain.java）

001	/*	<-	comment using //**
002	* To change this template, choose Tools \| Templates
003	* and open the template in the editor.
004	*/
005
006	package kototest;
007
008	/**	<-	comment using //**
009	*
010	* @author Koto
011	*/
012	public class KNMain {
013
014	/**	<-	comment using //**
015	* @param args the command line arguments
016	*/
017	public static void main(String[] args) {
018	// TODO code application logic here	<-	comment using //
019
020	System.out.println("Hello world!");
021
022	}
023
024	}

First we'll start with comments.

These yellow parts (with grey text)
are comments.

A comment is a specific
explanatory note for that item.
It is not a program.

Look, even if you make a program,
when you look at it later, you might
forget what you were doing, right?

If you write memos and explanations
within your program, then you'll have
some security.

Really, so you can write
memos inside your code!

That'll really help me.

How to write a comment

Method Usage

// The characters after "//" will become a
comment.
This can only be used to turn a single line
into a comment.

/*
*/ Enclose the part that you want to turn into a
comment with "/*" and "*/".

"/*" is the start, and "*/" is the end.
You can turn multiple lines into a comment.

Examples

// //++++++++++++++++++++++++++++
// Koto is an idiot.
// As a matter of fact, she's not sexy all.
// She also has no brains.
//++++++++++++++++++++++++++++

/*
*/ /* NAPO is a total genius. */

/* Oh yeah. He's a good-looking guy,
the most wonderful in the world. */

/*
+ By the way, that Koto chick
+ is completely hopeless. Just kidding.
*/

Hoho
Hoho

What the heck
is this!!

With Java, there's two ways for writing comments.
These methods use "//", or "/*" and "*/".

Each has their own place to be used, so make sure to use
them properly.

The parts that have been made into comments
won't be viewed as executable program by the
Java compiler. They'll be ignored.
So, you can write comments anywhere in the
source file.

In other words, no matter where you write these sentence,
they won't create errors.

If they annoy you that much,
practice writing your own
comments.

Can you actually
write a comment?

I won't show
you, though.

Alright!

Just you watch.

What do you mean!
Show me!
I mean, not that I
really care that much.

I bet you couldn't
even do it.

I did it!

And it definitely
went grey.
So then I deleted it~

What a shame, huh!

Other Structures

Hmmm…
Okay, so for now, is everything
fine other than the Main function?

For now we'll skip the other
entries in the picture.
It's fine if you just glance over the
contents of the picture.

Just leave them alone,
and don't rewrite them.

There's nothing immediately relevant
besides the Main function,
and this is closely related to classes,
so I'll explain them all together later.

There's, like,
all sorts of classes
there, huh.

In Java programming,
classes are important components
that affect the core.

But that part is a huge explanation
that's difficult to understand.

So let's go slowly and not get flustered.

Okay!

Slow and
steady wins the
race, right!

The flow of program run-time

Next, let's take a look at the
flow of program run-time for a
Java application, using this program.

At the same time let's look at the
Main function.

The flow of the program is something
like this.

Ooh,
so it's this sort
of flow.

	Run-time flow
1	The Java application runs. First the main function is invoked, and execution of the processes written within it begin.
2	The contents of the Main function block are run from the top in order. They are run one at a time, moving to the next one as each finishes. This time, the process that was run was to display "Hello world!" in the standard output.
3	When the processing is completed at the end of the block, the program finishes.

Simple,
right?

So it ends when
gets to the bottom…

This time, because there's only one command,
which is to display a message in the standard output,
it finishes once that's been run.

If there were multiple commands,
they would run in order from the top…
going to the next one as each finishes.

Main function (Main method)

This time, we wrote the
program in a section called the
main function (main method).

This is a special process that is
invoked at the beginning when a
Java application is run.

This is the starting point where
the run process of the application
starts.

You can only make one of these
in each Java application.

So it's special.

You write the program
inside it, right?

To put it another way
it's something
that's always required.

That reminds me,
I saw it last time.

Features of the Main function

* Only one can be written in each Java application.

* It is invoked at the start of the run-time.

Your first program code（KotoTest's KNMain.java）

001	/*
002	* To change this template, choose Tools \| Templates
003	* and open the template in the editor.
004	*/
005
006	package kototest;
007
008	/**
009	*
010	* @author Koto
011	*/
012	public class KNMain {
013
014	/**
015	* @param args the command line arguments
016	*/
017	public static void main(String[] args) {	<-	Main Function
018	// TODO code application logic here
019
020	System.out.println("Hello world!");
021
022	}
023
024	}

Ah yes, the program is written between
the brackets "{" and "}" of the
main function.
The range for these brackets is called a
'block'.

Be careful of the different brackets.
The brackets for the declaration part
are ( and ).
The brackets for the block are { and }.
You can't use [ and ].

A lot of different brackets are used with Java,
but each has a different purpose.
So be careful.

Blocks have to be
closed at the start
and finish using brackets.

The start of a block is
"{"

and the end of a block is
"}".

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