Summary: In this chapter, we will set up or developing environment and write our very first program! We will also set up our Text Adventure game and learn how to download/open the example code and Text Adventure stages.
It’s time to write our very first Java program! In order to do this, we need to make a project in IntelliJ. This project is where we will write and run our Java code. This section will walk you through making a new project in IntelliJ, so follow along! Note: the pictures shows in this section may be slightly different from what you see on your computer, depending on if there are any changes in the latest version of IntelliJ from the time of writing. You should still see the same basic parts no matter what.
Start by opening IntelliJ. If this is your first time, you will see a start screen like this:
Click on the “New Project” button. This will open a window where you decide what project and what version of Java you will use. Make sure “Java” is selected and that everything int he “Additional Libraries and Frameworks” panel is unchecked. IntelliJ should have automatically detected the JDK 17 we installed in [[00 Getting Started]]. If not, click the “Project SDK” dropdown and select “Add JDK”. Simply navigate to where the JDK is installed and select the JDK 17 folder. Once you have Java and JDK 17 selected, click “Next”.
We are not creating a project from a template, so leave that option unchecked and click “Next” again. One this page, we will choose the project name and where we want to save it. You are welcome to use the default save location or create your own. Below is an example with a custom save location and the name “examples”. Once you’ve selected a name and location, click the “Next” button.
You will now see a brand new, but empty, IntelliJ project! On the left you will see a “Project” panel. This is where we will put all of our code. In the center is a blank space where we will be able to open and edit our code files. At the top in a series of menus and buttons that we will explore throughout this book.
Now that we have our empty project, it’s time to add something to it! It is a tradition for a new programmer’s first program to be “Hello world!”, which is a program that will print out the words “Hello world!”. Simple, but effective! Start by right-clicking on the src folder 1 and select “New” -> “Java Class”.
A Java class is basically a file where our Java code lives 2. We will give this file a name of HelloWorld. Notice there are no spaces! Java class names cannot have spaces in them. Hit “Enter” and you will see our new class show up in the “Project” panel on the right and open in the center panel! Add the following code so your class looks like this:
1. public class HelloWorld {
2. public static void main(String[] args) {
3. System.out.println("Hello world!");
4. }
5. }Let’s break down what’s going on here. Line 1 tells us this Java file contains a class with the name HelloWorld. We also see a set of curly braces {}, with the opening brace on line 1 and the closing brace on line 5. Curly braces show belonging in Java and these are saying all the code inside this set of curly braces belongs to the class HelloWorld. Line 2 creates this chunk of code called a main method. This main method is the front door to our program and is where IntelliJ will start running our code. Again, we see a set of curly braces with the opening brace on line 2 and the closing brace on line 4. This means everything inside this set of curly braces belongs to the main method. Finally, line 5 is a code statement, which is a single Java direction for the computer to follow. Notice that this line ends with a semicolon ;. A semicolon is like a period in an English sentence, acting as a way to say that this Java statement is finished. This specific statement will print out the words “Hello world!”.
Now that we have everything typed up, it’s time to run our program! There are many ways to run a program in IntelliJ, so let’s briefly look at all the way. First, there are little green play buttons on lines 1 and 2 of the editing panel. We can click either one to open a menu and select the option “Run ‘HelloWorld.main()’”, and it even shows us the keyboard shortcut to do this. We can also select the “Run” menu from the top of the window and select the “Run” option from this menu.
You will notice that the “Add Configuration” box near the top right of the screen now shows the name of our class and a new green play button. We can now use this to run whichever class is in the box! Right now we only have one class, but in the future you will want to double check the class name.
We can now see a new panel, the “Run” panel, at the bottom of the screen that has the words “Hello world!”. Congratulations, this means everything is working! We’ve successfully made a new project, written our first Java program, and run that program! Try changing the words in double quotes and re-running your program to see how things change. You can even try adding more statements and see what happens!
Now that we know how to make a project, you can make a new project for each chapter of the book and follow along with the examples. However, we are also going to be working on a larger project throughout the entire book to put all of our new Java skills into practice. Let’s make a new IntelliJ project for this project! In our examples project, click on “File” -> “Close Project”. This will take us back to the welcome screen, but instead of a screen with only buttons to start a project we will now also see a list of our other projects we’ve recently opened. You can change the IntelliJ settings to either always open up to this page or to always open up to your last project by clicking on “File” -> “Settings”, going to “Appearance & Behavior” -> “System Settings” and modifying the setting “Reopen projects on startup”.
Throughout this book we will be making a text-based dungeon crawler game called Text Adventure. This project will allow us to put our Java skills learned in each chapter into practice, see how all the different skills fit together, and finish this book with a working Java program that can be shown to teachers, family, friends, and even future employers!
Walk through the same steps above and give your project the name “Text Adventure”. Once the new project is made, make a new class and call it “Game”. Next, add the the following code to your new class:
public class Game {
public static void main(String[] args) {
System.out.println("Welcome to Text Adventure!");
}
}Finally, run your code and make sure that you see the welcome message. You will use this same project for all chapters of this book and we will both make changes to this Game class and even write new classes! As we add more to this game, you might want to reference the code for this game and the chapter examples to see how they work, so let’s walk through how to download the code for this book and open it in an IntelliJ project.
The code for this book is available on a website called GitHub. You do not need to know how to use GitHub or git, which is the system that powers GitHub. All you need to know is the URL for each project and you can download a zip folder of all the code. There is a project for the chapter examples (https://github.com/BladeF/PlayfulJava-Chapter-Examples) and Text Adventure (https://github.com/BladeF/PlayfulJava-TextAdventure).
For each project, you will see a homepage and can explore the code on this website. You can also download the code to your own device by clicking the “Code” button and selecting “Download ZIP”. Move this folder to wherever you would like to keep it and unzip it. Once you’ve unzipped it, follow the directions for making a new project until you reach the name and location window. First, open the project location window and navigate to wherever you moved the unzipped code and select the folder that contains the “src” folder, which will be named either PlayfulJava-TextAdventure or PlayfulJava-Chapter-Examples depending on the project. Note: there will be two of these, one inside the other! Make sure to pick the inside one that contains the src folder, as shown in the image below.
Click the “Finish” button and IntelliJ will automatically make a project out of these Java files! You will notice something slightly different from what we did at the start of this chapter: inside of the src folder is another folder for each chapter. This is simply to make it easier to see all the code without having to know how to use git and GitHub; your projects do not need these folders. I strong encourage you to type each example and each modification to Text Adventure yourself, as this will help you learn the material much better, but you can use this code as a reference and to help troubleshoot your code if something is going wrong in your own projects.