CR Weekend Challenge

Integer i = 42;
int j = i;
^ that's perfectly fine though, they get auto-boxed and auto-unboxed

Integer i = null;
int j = i;
^ this would throw NullPointerException on the second line

retailcoder

And do classes have a default parameterless constructor?

Simon André Forsberg

yes

unless you specify one of your own

ClassName varName = new ClassName();

retailcoder

same as C# there.

can't be chained can they?

Simon André Forsberg

chained how?

retailcoder

1:06 AM

public SudokuDigit() : this(null) {
}

public SudokuDigit(Integer value) {
this.digit = value;
}

Simon André Forsberg

ah

retailcoder

I guess that's redundant in this case

Simon André Forsberg

public SudokuDigit() {
this(null);
}

public SudokuDigit(Integer value) {
this.digit = value;
}

retailcoder

this.digit would be null anyway

Simon André Forsberg

^^ that's how you do it in Java

retailcoder

1:07 AM

^^ lame.

:p

Simon André Forsberg

^^^ much more logical to me :)

retailcoder

so how do you call a base class (superclass?)'s constructor then? explicitly from the constructor?

Simon André Forsberg

super(parameters, params, 42);

public SudokuDigit(Integer value) {
super(value);
}

^^ for example

retailcoder

that's what I thought. So this means a derived type isn't garanteed to call the base constructor then?!

Simon André Forsberg

base constructors are always called

if there is an empty constructor available, that's called implicitly

otherwise, you MUST call one explicity or you'll get compiler error

retailcoder

1:11 AM

I'll stay away from inheritance for now

Simon André Forsberg

lol

retailcoder

^^^ good to know

Simon André Forsberg

it's not that dangerous actually :)

retailcoder

meh.. I don't have a prospect for now :)

would this be a valid comment at the top of a constructor:

/// creates a new, empty value

Simon André Forsberg

depends on if you want to use "javadoc", which is a good way of commenting methods and stuff

retailcoder

1:14 AM

that was the intent..

Simon André Forsberg

javadoc begins with /** and ends like normal comments with */

/** creates a new, empty value
*/
public SudokuDigit(Integer value) {
super(value);
}

or you can of course put it on the same line, but it must end with */

retailcoder

works. Thanks!

@SimonAndréForsberg how do I throw new InvalidOperationException();?

Simon André Forsberg

UnsupportedOperationException

otherwise it's correct

retailcoder

(bitches at lack of auto-complete)

Simon André Forsberg

Ctrl + Space

I believe there's a way to auto-activate it as well

somehow

among all the million Eclipse settings :)

retailcoder

1:19 AM

lol

Missing setting: "Make my IDE work like VS"

Simon André Forsberg

I'll probably miss the setting "Make VS work exactly like Eclipse" in VS :)

retailcoder

So far so good?

/** Sets the current value of the digit.
* Specify Null for no value.
* Throws UnsupportedOperationException if value is not valid.*/
public void set_Digit(Integer value) {
if (!validateDigitValue(value)) throw new UnsupportedOperationException();
this.digit = value;
}

private Boolean validateDigitValue(Integer value) {
return value == null || (value >= 1 && value <= 9);
}

Simon André Forsberg

validateDigitValue can return primitive boolean

retailcoder

ugh. at first I was returning bool but it didn't like it..

thanks, that was the intent :)

Simon André Forsberg

otherwise it's quite good :) not 100% Java conventions, but I gotta save something for the review ;)

although please rename method to setDigit

retailcoder

1:26 AM

Done ;)

Simon André Forsberg

good

retailcoder

Gotta make some coffee!

Simon André Forsberg

Window -> Preferences -> Java -> Editor -> Content Assist

there's your settings for auto-complete, @retailcoder

retailcoder

Amazing! I learned my entire VB6 with IntelliSense!

(and MSDN)

Simon André Forsberg

for Java, Oracle's documentation will be your friend:
http://docs.oracle.com/javase/7/docs/api/java/util/ArrayList.html

the java.util package contains a whole bunch of classes you'll probably look for sooner or later

docs.oracle.com/javase/7/docs/api/java/util/…

retailcoder

1:38 AM

uh, Sudokudigit[9,9] isn't legal??

Simon André Forsberg

SudokuDigit[][] varName = new SudokuDigit[9][9];

retailcoder

So all multidimensional arrays are jagged arrays?

Simon André Forsberg

yup, unfortunately

retailcoder

I'm being a PITA right?

Simon André Forsberg

You really want me to respond to that, @retailcoder?

Current Weekend Challenge: Sudoku Solver

2

^ time to change the pinned message

and perhaps time to remove that you and Jamal can pin them? :P

retailcoder

1:42 AM

Thanks, forgot about that

done.

Simon André Forsberg

yay ^^

nice

retailcoder

Still can't accept the answer on WC#3

yet

Simon André Forsberg

haha

then it's still not time for me to start coding :P

time for me to take a shower though, then I'll be back for a short while and then it's bedtime

retailcoder

so if I want to get the length of SudokuDigit[][] digits, I go digits.lengthand that gives me the length of the 1st dimension; and then I go digits[i].length to get the length of each "row"

Simon André Forsberg

yup

retailcoder

1:47 AM

FML

Simon André Forsberg

2:12 AM

@retailcoder oh, what's the problem?

Any last-minute questions for me?

retailcoder

hmm anything other than jagged arrays for a 9x9 thing?

nevermind

this is my hello world

I need to start with arrays

right?

Simon André Forsberg

yes, you need to start with arrays

retailcoder

I'm so abusing UnsupportedOperationException

Ignorance is bliss!

Simon André Forsberg

or you could use ArrayLists I suppose :) But you can definitely expect @rolfl to comment on that in the review, if you do :)

retailcoder

lol

Simon André Forsberg

2:16 AM

why are you abusing it? Writing all the signatures for your methods first and just throwing it until you bother writing the actual implementation?

retailcoder

public SudokuDigit[] getRow(int row) {
if (!validateGridIndex(row)) throw new UnsupportedOperationException();
return this.digits[row];
}

^^ this

I should just let it throw some "out of range" exception right?

Simon André Forsberg

either skip the check and let it throw ArrayIndexOutOfBounds automatically, or you could use IllegalArgumentException

retailcoder

Yeah I'll skip the check. It's not like me to put guard clauses everywhere like that

Simon André Forsberg

I expect that you're smart enough to avoid that that happens anyway

you won't call getRow(42) anyway, will you?

retailcoder

:)

Bottom line, don't do in Java what you wouldn't do in C#

Simon André Forsberg

2:20 AM

exactly

retailcoder

^^ flip that & remember it when you do your C# :)

Simon André Forsberg

Should the current weekend challenge be shown in VERY BIG LETTERS somehow in this question? Like at the top of the question or something?

oh yes, I will :)

Although I'm not so sure it applies for C#... In Java, I wouldn't use LINQ... In C#, why not?

retailcoder

Oh you would if Java had it!

So an array is nothing special in Java right?

Simon André Forsberg

Yeah, I suppose :)

retailcoder

I mean, it's not an object that implements some IEnumerable interface

Simon André Forsberg

2:25 AM

depends on what you mean by "special"

retailcoder

^^ that

Simon André Forsberg

no, but you can use for-each on it

retailcoder

ooh

that just made my day

/sarcasm

Simon André Forsberg

for (SomeClass obj : array) {
...
}

retailcoder

:)

wait, that's a foreach?

Simon André Forsberg

2:26 AM

yup

retailcoder

wtf

I don't get the syntax

Simon André Forsberg

simple, huh? :)

SomeClass[] array = new SomeClass[42];
...
for (SomeClass obj : array) {
...
}

retailcoder

so obj is your iteration instance!

Simon André Forsberg

yes

couldn't be easier :)

retailcoder

putting that in practice just right now (implementing getColumn)!

Simon André Forsberg

2:29 AM

just out of curiosity, do you use digits[row][column] or digits[column][row]?

retailcoder

/** Sets the value of specified grid coordinates. */
public void setDigit(Point coordinates, Integer value) {
this.digits[coordinates.x][coordinates.y] = new SudokuDigit(value);
}

/** Sets the value of specified grid coordinates. */
public void setDigit(Point coordinates, SudokuDigit value) {
this.digits[coordinates.x][coordinates.y] = value;
}

(I'll end up deleting one of the two, just not sure which one yet)

Simon André Forsberg

lol

retailcoder

I got it reversed?

Simon André Forsberg

ok, you use [x][y] at least, same as I do

your methods look fine :)

retailcoder

what's funny then? :/

Simon André Forsberg

2:31 AM

that you are not sure which one to delete :)

retailcoder

.oO(I'll probably delete the Integer overload)

...no... I'll probably delete the SudokuDigit overload

...

FML

Simon André Forsberg

haha

I'm honestly not even sure myself which one to keep

small suggestion though: One of them should call the other

retailcoder

right. that's what C# me would do :)

Simon André Forsberg

Then I think your Java you should do it also

retailcoder

So much better!

/** Sets the value of specified grid coordinates. */
public void setDigit(Point coordinates, Integer value) {
setDigit(coordinates, new SudokuDigit(value));
}

/** Sets the value of specified grid coordinates. */
public void setDigit(Point coordinates, SudokuDigit value) {
this.digits[coordinates.x][coordinates.y] = value;
}

Simon André Forsberg

2:36 AM

yup

retailcoder

Look mama, I'm coding in Java!!

talk about a super-sophisticated and over-engineered Hello, World!

@Jamal ^^

@SimonAndréForsberg another thing: if I do SudokuDigit[] result = new SudokuDigit[9];, have I just created a 10-slots array?

Simon André Forsberg

nope, you will have indexes 0 1 2 3 4 5 6 7 8

9 slots

retailcoder

cool.

Simon André Forsberg

yeah, can't do that in C#, can you? </sarcasm>

retailcoder

lol I'd never even initialize a feakin' array in C#!

Simon André Forsberg

2:41 AM

oh, ok :)

retailcoder

LINQ dude, LINQ!!

Simon André Forsberg

haha

I'll probably totally forget about that when starting C#

retailcoder

(miss it already!)

It's ok, I'll remind you when I review your code!

Simon André Forsberg

Well, C# doesn't have guava I believe :)

retailcoder

pffft. it's in the core libs.

Simon André Forsberg

2:42 AM

When used correctly, Guava is quite powerful. Although not as powerful as the upcoming Java 8 features of lambda expressions of course

haha

you just gotta be aware of them I guess

retailcoder

Just so you know, LINQ is a set of extension methods (C# 3.0+) that extend any type that implements IEnumerable - that includes all arrays, List, Dictionary, and pretty much anything that can be iterated.

Works with lambdas

Simon André Forsberg

yeah, I'm aware that it works with Lambdas

will be interesting

gotta sleep for now

3:45 am. Dammit.

retailcoder

ouch!!

well thanks!

Simon André Forsberg

blames the fact that @retailcoder is learning Java

night

retailcoder

good night!

retailcoder

3:19 AM

LONG LIVE STACKOVERFLOW!!!

rolfl

3:52 AM

@retailcoder still alive?

retailcoder

yup

rolfl

Just set my Ding!

You planning on being up for a while?

retailcoder

@rolfl ding!

rolfl

loud and clear.

retailcoder

yeah, although I don't think I'll finish tonight :)

rolfl

3:53 AM

Watched a 3 episode Mentalist marathon with my wife.

HUsbandly duties done.

Free to help now.

retailcoder

So you do have a life!

rolfl

Maybe I will start a Sudoku project.

retailcoder

thanks!

rolfl

Time to close down three other eclipse environments (bye-bye.... watson).

If you want my attention, make it ding, otherwise I'll probably not pay attention here.

retailcoder

ok!

@rolfl (ding!) why do I get an error here in `public class GridValidator implements ISudokuValidator`:

@Override
public boolean hasAllDigits(SudokuDigit[][] region) {
// TODO Auto-generated method stub
return false;
}

^^ it says "method must override or implement a supertype method".. wtf?

rolfl

4:02 AM

Not sure, what's...

Ahh, the @Override annotation indicates this method overrides an inherited method.

If the interface does not have a method with that signature, then you can't use Oberride.

retailcoder

The genius IDE put that in automatically...

rolfl

It probably means you changed something's name/type ....

retailcoder

how do I implement an interface then?

rolfl

You appear to have done it right:

    public class GridValidator implements ISudokuValidator {
        @Override
        public boolean hasAllDigits(SudokuDigit[][] region) {
            return false;

But ISudokuValidator needs a method:

public boolean hasAllDigits(SudokuDigit[][] region);

retailcoder

ugh.. ISudokuValidator wasn't saved.

rolfl

4:05 AM

^^^ 'abstract method'.

retailcoder

And that's a smart IDE??!

rolfl

Actually, yes ;-)

Ctrl-Shift-S saves all.

retailcoder

note to self: hit Ctrl+S like a paranoid fearing an imminent power outage.

rolfl

You don't do that when editing something in Word?

retailcoder

nope. And I don't do that in VisualStudio either (and it did bite me more than once!)

retailcoder

4:34 AM

@rolfl is this normal?

import java.util.HashSet;
import java.util.Set;
import concrete.SudokuDigit;
import interfaces.ISudokuValidator;

rolfl

Not really, no.

retailcoder

what is?

rolfl

For this challenge, I expect you to use just one package.

retailcoder

...

rolfl

Let me explain...

An import is only needed when the resource you need is in a package that is not your own package.

retailcoder

4:36 AM

could I just import java.util;?

rolfl

Yes.

Type Ctrl-Shift-O

It will 'organize imports'.

What's left?

retailcoder

package concrete;
import interfaces.ISudokuValidator;

import java.util.HashSet;
import java.util.Set;

rolfl

This task is not likely going to be more complicated than will need to fit in one package.

retailcoder

import java.util; doesn't work

rolfl

A package typically has a 'unique-to-the-person' name, like com.ibm..... or com.oracle....

No, that will not work, but: import java.util.*; will.

retailcoder

4:39 AM

ah-ha!

rolfl

I would expect your ISudokuValidator and your SudokuDigit and all the classes you create to be in just one package.

Simething like 'retailcoder.sudoku

retailcoder

ok I'll move them then. It's just this habit I have of starting a C# project with creating, say, a RetailCoder.Sudoku.Abstract namespace for abstractions, and a RetailCoder.Sudoku.Concrete namespace for implementations.

rolfl

You can easily move classes in eclipse by being in the class and 'Alt-Shift-V' (v-for-moVe)

retailcoder

lol. obviously!

rolfl

In that fialog it will even let you create a package.

It will make things easier for you if you have all your code in one package

retailcoder

4:41 AM

I guess so

but if I do import java.util.*; and then ctrl+shift+o it replaces it with the specific ones I'm using.

rolfl

Here's a picture of My Package ;-)

@retailcoder - yes, it will. It is 'best practice' to import only what you need.

retailcoder

how do I know if the project still builds?

rolfl

If you use Eclipse's autocomplete (Ctrl-space) it will automaticlaly add anything to the imports.

There's no red X's like I have on my Grid.

retailcoder

If there's nothing in "Problems" there's no problem anywhere in the project?

ah ok I see it

rolfl

Problems can be configured.... by default it is workspace-wide... but you can change it to be on whatever-is-selected, and it's children.

retailcoder

4:47 AM

@rolfl ^^ what I have so far :)

rolfl

Great... no warnings or errors.

You will probably want to remove the 'Sudoku' from the start of all your classes ... but that's purely cosmetic.

Everything in retailcoder.sudoku is something Sudoku.

retailcoder

yeah makes sense.. if I want to write a test, I just create a class with a void main()that calls my code?

is there not something more.. structured?

rolfl

Officially I should recommend jUnit for tests.

You may just want to start with a main-method anyway.

retailcoder

and officiously?

rolfl

actually... start right!

OK, follow along:

Right-click on our project 'SudokuSolver'.

Choose the 'new Source Folder'.

Type 'tests'.

you shoul dnow have src and tests ... right?

retailcoder

4:52 AM

yup

new junit test case?

rolfl

OK, in tests, create a package retailcoder. .... uh-huh!

you got it.

retailcoder

exactly why do I need a "package"?

rolfl

It's a namespace.

retailcoder

but then why can I add a "loose" class/interface/enum/whatever in there?

rolfl

So that both you and I can have a class called Sudoku, and they're different.

That's the default package .... bad practice.

retailcoder

4:54 AM

ok

rolfl

(although it is convenient when you are doing quick things without an IDE.

Create a package in your tests source folder... can be the same as your other package (should be the same).

retailcoder

oh.. I called it retailcoder.sudoku.tests :)

rolfl

That's OK, but there can be some advantages to using the same package name.

You won't need to lnow that for a while though.

retailcoder

not gonna ask about UI stuff, but is there a Console I can output to?

rolfl

It's on the bottom there, bottom right....

Maybe not shoing yet, @retailcoder

Window-show view-> console.

retailcoder

4:57 AM

Ah!

rolfl

It is output an input.

s/an/and/

retailcoder

well I'd hope so!

:)

I can't rename the test namespace to retailcoder.sudoku, says it conflicts with the other one...

Package 'retailcoder.sudoku' already exists in this project in folder 'src'

..but it allows me to 'continue'.. not sure it's a good idea

^^ @rolfl

rolfl

No.,

retailcoder

no, not a good idea?

rolfl

typing ... wait.

when you create package a.b.c.d you automatically also create a.b.c, a.b. and a

The question is just how you find them in eclipse.

retailcoder

5:00 AM

bah, I'll just keep it as is, no harm done.

hi @Jamal

Jamal

Hi.

retailcoder

learning Java, I am :)

Jamal

Wait, this isn't the general room...

retailcoder

lol

lost?

rolfl

Nope...

Jamal

5:02 AM

I just saw "5s" on there (indicating that someone is talking now), and I joined the room.

retailcoder

There is no general room anymore - it's The 2nd Monitor now :)

Jamal

Whatever. :-P

rolfl

OK, @retailcoder... see this picture

My free-hand sucks.

drop that down, choose 'filters',

Un-check the 'Empty Parent Packages'

retailcoder

what does that do?

rolfl

Have a look at your tests area now.

retailcoder

5:04 AM

oh

rolfl

Now you can 'easily' create tests in your retailcoder.sudoku package

retailcoder

and I deleted the .test and it wiped everything but the default package.. then I recreated retailcoder.sudoku under tests and ...no complaints :)

rolfl

ok.

When you create a JUnit test, create a class called TestXXXXX where XXXX is the name of the class you want to test, and then also select that class in the dialog too.

retailcoder

Is a JUnit Test Case actually a class?

rolfl

It will create test-stub methods matchin all the methods in the class you want to test.

yes it is.

It is a class with naming conventions (and annotations) that the JUnit test harness understands.

It can 'inspect' the class and automatically find the tests to run.

retailcoder

5:12 AM

Ugh. Is "testClassNameMethodName" a convention of some kind, or I can name my tests as I want them? I don't want just 1 test per method!

rolfl

You can name thenm whatever you want.

Do you have the @Test annotation above?

(above the method?)

@retailcoder ?

retailcoder

yup

rolfl

OK, that's JUnit 4, which is good.

The only thing you need is that.

Whatever is marked with that will be tested.

retailcoder

wow I'm such a noob!

note to self: stop thinking in .net!!

rolfl

That's OK, sersinsly.

retailcoder

5:16 AM

^^ is that a typo or it's another word I need to lookup?

rolfl

typo.

2

retailcoder

seriously

retailcoder

5:32 AM

room topic changed to CR Weekend Challenge: A room to discuss weekly code challenges to be posted as CR questions for review [addicted-to-cr] [fun] [get-it-done-fast-trap] [weekend-challenge]

rolfl

5:54 AM

Let's see if this works....
╔═══╤═══╤═══╦═══╤═══╤═══╦═══╤═══╤═══╗
║   │   │   ║   │   │   ║   │   │   ║
╟───┼───┼───╫───┼───┼───╫───┼───┼───╢
║   │   │   ║   │   │   ║   │   │   ║
╟───┼───┼───╫───┼───┼───╫───┼───┼───╢
║   │   │   ║   │   │   ║   │   │   ║
╠═══╪═══╪═══╬═══╪═══╪═══╬═══╪═══╪═══╣
║   │   │   ║ 3 │   │   ║   │   │   ║
╟───┼───┼───╫───┼───┼───╫───┼───┼───╢
║   │   │   ║   │   │   ║   │   │   ║
╟───┼───┼───╫───┼───┼───╫───┼───┼───╢
║   │   │   ║   │   │   ║   │   │   ║
╠═══╪═══╪═══╬═══╪═══╪═══╬═══╪═══╪═══╣

retailcoder

@SimonAndréForsberg @rolfl I see what you mean with Eclipse being a great IDE: I see lots of functionalities that I use with ReSharper in Visual Studio. And VS without my R# feels... I see what you mean.

rolfl

@retailcoder in one of your classes, type Ctrl-shift-F (for format) ... it will re-format everything in standard Java conventions .... (if you don't like it, type Ctrl-Z to undo).

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