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Using Dependencies
7:48So now that you have the dependencies, how do you use them?
Okay, so now that we have
our dependencies defined and
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we've run the Gradle command to download
them, it's actually really simple to use.
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You just import it to a file and use it.
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What might not have been clear is that
as long as you've checked in your
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Build Script using Git or another version
control tool, Anyone who has a copy
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of your source code can now run
the Build command on their computer and
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get the same version
dependency that you specified.
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Pretty cool, right?
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No need to check in the JAR files,
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because they can get installed
the same way that we did.
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So this opens up a whole new
world of APIs to us, right?
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Let's first go play with our new library,
and then poke around and
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see what else is out there.
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Okay, so let's make a new class in
our source main Java directory here,
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let's make a new class, and
let's call it, main right?
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We'll make the first file
just to play around, so
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we'll call it com.team
treehouse.reviews.Main.
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And then we'll click okay.
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I have set up some version control here,
so I'm just gonna go ahead and
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automatically check that in.
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Okay so, here's our Main class here and
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let's just write up
a quick prove of concept.
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Let's imagine that our app allowed
reviews of different code snippets.
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So what we want here is we wanna provide a
way to export the data, those reviews, and
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then later import it into a spreadsheet
to make further graphs and things.
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So this is actually a pretty
common request, and
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the good news is we really don't
have to do that much, right?
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Cuz we already have this library.
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So let's do this, let's just go ahead and
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let's start out with our public
static void main method.
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And let's just start talking
about the CSVPrinter object.
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So the way that you do that is
you just start typing, right?
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So CSVPrinter, oh there it is,
that's what we want, CSV Printer, okay?
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And we'll call that a printer,
and we'll make a new one of them,
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and I'm not exactly sure what that is, but
let's just see what it comes back with, so
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it says it needs an appendable called out.
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So this is just a proof of concept but
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I happen to know that the system.app
where we normally print the console.
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That implements the appendable interface,
so let's do that, so
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system.out is the first parameter here and
the next thing I was looking for
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was a format, right?
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So it's a CSV format and
we'll make it excel format,
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cuz that's what they're
gonna be looking at here.
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Right, so we got a little red mark here,
let's see why.
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Let's surround that with a try and
a catch.
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We'll just leave that as the default here,
this is again just a quick little mock up.
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Okay so let's add,
let's write this stuff out.
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So I'm gonna type printer.printRecord,
I saw that that was available, right?
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I saw that was available when I
was looking at the documentation.
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But I don't remember exactly how to
use it, so now I could press F1, and
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look at that, all the help is here
because it's in the Java doc.
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Okay, so we just, we put in
the different values that we want, and
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it takes in an endless amount of objects.
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So it'll print, oh that's cool,
so I can print out,
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not only can I print out the string.
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So let's say that we had, we'll just
make a couple of fake reviews here.
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So I totally thought that that code
was five and I said that, I love it,
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five out of five, right?
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And then let's do another one and
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we'll do printRecord, and we'll say
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that Chris, our other Java teacher here.
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If you haven't seen his stuff yet,
it's great.
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He gave it a 4 though,
and he says pretty good.
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Would be better with an annotation or two.
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I noticed he used a comma in his review,
and that's kind of the edge case that we
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were talking about,
that was a problem before right?
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So, the other thing that's kind of cool
that I also wanted to show you real quick,
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is that you can also navigate
to the source, right?
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So if I Cmd+B that or Ctrl+B.
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I can actually look and
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see how the codes happening because
it's an open source, pretty crazy right?
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All right, so
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we're back here, we're in our file, it
automatically gets those imports for me.
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I don't know if you saw that pop up.
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So I think if we scroll down here and
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we run it we should be all good,
let's see what happens.
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We'll say run, we'll run main.
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I forgot a semicolon, there we go.
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Now let's go ahead and run that.
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Here we go, see, it's comma separated and
notice that when the comma happens,
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it put it in quotes.
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This is how Excel format allows you to
have the separator inside the text, but
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this did it for us.
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Note how it knew about strings and
numbers,
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that we didn't have to
think about any of that.
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It just did it all for us.
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Just a few lines of code, right?
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This is just the beginning of
your open source adventures.
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So this example that I kinda walked you
through works pretty well if you know
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exactly what you're looking for.
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And I kinda did, right,
I showed you this library.
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But what if we're looking for
something less specific.
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For example, let's think about adding
some more cool features to our project.
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I think it would be great if
we could go to any website and
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pull information from it.
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Like with these code
snippets that are there.
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Let's go to a website, pull that code
snippet down if it didn't have API.
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So now I could probably
write this myself right?
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I understand how HTML tags work and
everything like that.
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But first, I think we should check
if something else is out there
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that does this.
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So, what I would do is I would search and
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say how do you do this and
then I come across some technology.
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Now it might not be specifically in
my language, and, so it says, oh,
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it sounds like you are talking about an
HTML parser or something along those line.
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So that is what I want, so
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now logically you'd think that I can
just go search Maven for that right?
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So let's try that, let's go over here,
this is search.maven.org.
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So I'm going to search for html parser.
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That comes back with something.
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Oh, it says it hasn't
been updated since 2010,
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the last html parser written was in 2010.
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Not true, this search is a little bit off.
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Now, your other favorite java teacher,
Chris, wanted to make sure
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that I shared his technique with
how he does things like this.
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So what Chris does is he goes to
Google and he searches just for Maven.
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And then what are you searching for?
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So, html parsers, so he does that.
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And you'll see that there's this great
thing here called www.mvmrepository.com.
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Now mvm is the word for Maven shortcut,
that's kind of how it goes.
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This is a little open source website
that indexes the Maven site.
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So here is one, htmlparser.jar.
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We could take a look at
it if we wanted to, and
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see that it was created on 2011,
that's okay.
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Let's go ahead and let's search this site,
this site looks pretty good.
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It may have it in repositories,
so HTML parser.
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Oh here's one called Jsoup and it shows
you how many people are using it, 335.
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So that looks pretty nice.
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So open this up, and here, oh,
August 2015, that's great.
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It's been updated recently,
I think we should use this one.
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Let's use J suit.
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So I'd use Jsoup, and that's how right?
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I'd just come over back
to our dependencies and
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I'd pop it in our deps right here.
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Deps is the cool way to say dependencies.
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Also remember that the majority of active
open source project code is actually now
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on GitHub and
GitHub uses a thing for stars right?
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So you can come in and you can search for
language colon Java or
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whatever they're over
here on the side too.
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And if you sort by most stars,
you'll see the most popular.
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And you can cruise around here and
see what's out, and see what you find and
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share it in the community with us.
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And also, don't forget that when
you see these, you can contribute.
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If you see a spelling error, fix it.
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You can do that.
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That's a different lesson, though.
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