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Kotlin for Java Developers

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Creating the Project

4:22 with Ben Deitch

In this video we'll start with a quick overview of solitaire, and then we'll create the project!

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Kotlin Koans are essentially Code Challenges provided by IntelliJ to help us learn Kotlin. If you're ever looking for more practice definitely check out the Koans!

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    Before we get started with building the app, 0:00
    let's make sure we're all on the same page about what Solitaire is and how it works. 0:02
    Solitaire, also known as Patience or Klondike, 0:08
    is a card game that you can play all by yourself. 0:11
    Here's a quick overview of how we'll be playing. 0:14
    We start by creating the tableau, which contains seven piles of cards. 0:17
    The last card in each pile is placed face up, and 0:21
    each pile has one more card than the last. 0:25
    Once we've created the tableau, 0:28
    the remaining cards are placed up here to become stock. 0:30
    And when we want to draw a card, 0:33
    we just flip it over into what's known as the waste pile. 0:35
    But don't worry about throwing cards into the waste pile. 0:38
    If we ever run out of cards in our stockpile, 0:41
    we'll just recycle the waste to give us a new stock. 0:44
    The goal of Solitaire is to move every card in the deck 0:47
    up to these four foundations. 0:50
    The catch is that each foundation corresponds to only one suit, and 0:53
    you need to build up each foundation from the bottom starting with the ace. 0:57
    There's also a catch when dealing with the tableau piles. 1:02
    If we want to add a card to the tableau, its value needs to be 1:05
    one lower than the card above it, and it also needs to be the opposite color. 1:09
    So if we have a nine of hearts as the last card and one of our tableau piles, and 1:13
    we just turned over the eight of clubs into the waste, 1:18
    we can play that eight of clubs right below our nine of hearts. 1:21
    Also, if a tableau pile is empty, only a king is allowed to fill the void. 1:25
    All right, if you're still not quite sure what's going on, 1:30
    there's a link in the teacher's notes below to an online Solitaire game 1:34
    that works just like ours will. 1:37
    Now that we know how to play the game, let's get down to business. 1:40
    For this course, we're only going to deal with the game logic. 1:44
    That is, we won't be adding a user interface. 1:47
    This way, we can use the same code for an Android app and a JavaFX app. 1:50
    The only thing that'll be different is the UI code. 1:56
    Also, since we won't be adding a UI, rather than use Android Studio, 1:59
    we'll be doing all of our programming in IntelliJ IDEA. 2:04
    So let's open up IntelliJ and get started. 2:07
    The first thing we need to do is create the project, so 2:10
    let's click Create New Project. 2:13
    Then, on the left, pick Kotlin for the JVM, and hit Next. 2:15
    Then let's name the project, Solitaire. 2:22
    And hit Finish. 2:27
    Hooray, you're your first Kotlin app. 2:30
    Now, let's drill down to the source folder. 2:33
    And, bummer, it doesn't look like it gave us a main class. 2:36
    But, no worries, we can just make our own. 2:39
    Let's right-click on the Source folder, and choose New>Kotlin File/Class. 2:42
    Then let's name it App, and hit OK to give us our first Kotlin file App.kt. 2:48
    Next, we need to provide an entry point end to our Kotlin application. 2:55
    Over in App.kt, let's type main, and then hit tab to generate the entry point. 2:58
    And there we go. 3:05
    Now, let's quickly run this to make sure everything's working. 3:06
    But before we can run anything, we'll need to create a run debug configuration. 3:09
    Luckily, IntelliJ makes this really easy for us. 3:14
    Just click the Kotlin icon in the gutter next to our main function, and pick Run. 3:18
    Then, IntelliJ will create a configuration for us and run the app. 3:25
    Nice. 3:30
    Now that everything's up and running, let's talk about that main function. 3:31
    The first thing to note is the fun keyword. 3:34
    All functions in Kotlin are declared with the fun keyword. 3:37
    Then comes the name of the function, main. 3:41
    And then inside the parentheses are any arguments. 3:44
    Unlike Java, the name of the argument comes first, 3:47
    followed by a colon and then the type, array of strings. 3:51
    And if we wanted to return anything, we would add a colon 3:56
    after the parentheses, and then specify the return type. 4:00
    In Kotlin, instead of using void, we use Unit. 4:05
    And just like in Java, we usually omit this for 4:09
    functions that don't return anything, so let's undo that. 4:12
    And now that we've got our entry point handled, 4:17
    in the next video we'll start working on the game. 4:19

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