In order to learn the Java programming language we need to install two things: the Java language itself and a tool to write Java. It might seem a little weird to think about installing a language, but think about it like teaching the computer to understand Java just like you might take a course to understand German. Once the computer can understand Java, we need a tool to write and run our code. Technically, we gain those tools by installing Java, but those can be a bit difficult to use. Instead, we’re going to install a tool that will let us write and run all our code in one place! If you’re interested in learning how to run your code with the native tools, check out [[Appendix A - Java in the Command Line]].
Let’s start by installing Java. Java is currently developed by the company Oracle, but there is also an open-source version of Java called OpenJDK. We are going to use this one because it is free to use in all sorts of projects.
We’re not going to dive too deep into how Java works on the inside in this book, but there are two terms that are important to know: JDK and JRE. These are two ways to work with Java, depending on what you’re trying to do. JRE stands for Java Runtime Environment, and it contains all the files necessary for running Java code, including software written in Java. JDK stands for Java Development Kit and contains al the files necessary for writing Java code. A JDK automatically comes with a JRE, but a JRE does not come with a JDK.
That might be a bit confusing, but all you need to know is that you might have a JRE already installed on your computer to be able to run certain programs. We need to install a JDK to be able to write Java code ourselves. Now, there might be some issues if you already have a JDK installed! That will be addressed in the section for each operating system below.
There are many different versions of Java, so which one do we want to use? In this book, we’re going to explore Java 17. Of the many versions of Java, all of which are numbered, certain versions are given long-term support, or LTS, status. These versions are major versions that will be supported for several years. As of this writing, there are three LTS versions of Java: 8, 11, and 17. Java 17 was released in September 2021 and will be supported until September 2026. It also has some pretty cool improvements from Java 11!
That being said, a new version of Java is released relatively often, roughly on a six month schedule, so there will most likely be a newer version of Java than Java 17 by the time you are reading this book. That is okay! Simply download the latest version of Java and it will have all of the features you will learn here.
We can download the latest Java JDK from the following website: https://jdk.java.net/. Find the right section below based on your computer and follow the directions on how to install Java on your operating system. Note: directions are provided for how to work with Java in the web, which can be used if you use a Chromebook or are using a computer that you can’t install things on, like a library computer, but the directions are very different from the personal computer directions.
Start by downloading an unzipping the Windows/x64 build. This will get a you folder something along the lines of openjdk-17.0.2_windows-x64_bin. Inside this folder is another folder called something along the lines of jdk-17.0.2. Note: the second and/or third number may be different, but the most important part is that is starts with 17. Next, open File Explorer and navigate to C:\Program Files. Make a new folder here called Java. Move the jdk-17.0.2 folder from your downloads into the new Java folder. If done correctly, you should have something like this:
Now that we’ve put the JDK in the correct spot, we need to tell Windows how to find it. Open the start menu, search for “environment variables”, and click the result “Edit the system environment variables”. This will open a System Properties window and click on the Environment Variables button in the bottom right:
In the System Variables part of the window, either create or edit the JAVA_HOME variable with a value of our new Java folder: “C:\Program Files\Java\jdk-17.0.2”. Next, edit the Path variable and add a new row with the value %JAVA_HOME%\bin. Once this is done, restart your computer to allow the operating system to read these changes. Note: if you have another JDK installed and you don’t need it, go ahead and delete the folder for that JDK. If you do need it, you will need to do some more complex setup that will not be covered in this book.
Once your computer has finished restarting, open PowerShell and type in the following command:
PS> java -version
openjdk version "17.0.2" 2022-01-18
OpenJDK Runtime Environment (build 17.0.2+8-86)
OpenJDK 64-Bit Server VM (build 17.0.2+8-86, mixed mode, sharing)If you see something like the above message, then everything is all set and ready to go! If not, go back and follow the directions again, checking for anything that doesn’t match up.
There are two different versions of the Mac JDK. The version you choose will depend on the type of Mac you have. If you have an Intel-based Mac, you will download the macOS/x64 JDK. If you have an M1-based Mac, you will download the macOS/AArch64. You can find out which type of Mac you have by clicking on the Apple icon in the top left of the screen, selecting “About This Mac”, and looking at the “Chip” information. Once you have the correct JDK downloaded, it’s time to install it. There are two potential ways, depending on your comfort level with the Terminal environment.
If you’re not comfortable using Terminal, the JDK can be installed using Finder. Start by navigating to your Downloads folder an expand __openjdk-17.0.2\_macos-x64\_bin.tar.gz__ by double-clicking on it. Note: the second and/or third number may be different, but the most important part is that is starts with 17. This will give us the folder jdk-17.0.2.jdk. Move this new folder to Macintosh HD -> Library -> Java -> JavaVirtualMachines. You will be prompted to enter your computer password to complete this move.
Finally, open Terminal and run the following command:
$ java -version
openjdk version "17.0.2" 2022-01-18
OpenJDK Runtime Environment (build 17.0.2+8-86)
OpenJDK 64-Bit Server VM (build 17.0.2+8-86, mixed mode, sharing)If you see something like the above message, then everything is all set and ready to go! If not, go back and follow the directions again, checking for anything that doesn’t match up.
If you’re comfortable using Terminal, we can use scripting commands to expand the tarball and move it to the correct location. You will be prompted to enter your computer password to complete the moving process. Enter the following commands to do this:
$ cd ~/Downloads
$ tar -xf openjdk-17.0.2_macos-x64_bin.tar.gz
$ sudo mv jdk-17.0.2.jdk
$ java -versionInstalling Java on Linux can happen in several ways. We will show you how to install Java using the package manager on Debian/Ubuntu-based and Red Hat-based systems. Java can also be installed manually using the Linux tarballs available on the OpenJDK website, but that is not covered in this book. If Java 17 is not available on your distribution of Linux and you do not want to use Java 11, then you can find directions on how to do this process for your specific Linux distribution.
The latest editions of Ubuntu and Fedora at the time of writing, which are 20.04 and 35, respectively, support Java 17 and have JDK 17 packages available in their package manager. If you are on an older version of these operating systems, you can work through 95% of this book using Java 11. Throughout this book I will notate the topics that are Java 17 specific and show how things were previously done in Java 11, which means you will be able to follow along and complete the project using Java 11 strategies.
Open the Terminal application and run the following commands:
$ sudo apt-get update
$ sudo apt-get install openjdk-17-jdk
$ java -version
openjdk version "17.0.1" 2021-10-19
OpenJDK Runtime Environment (build 17.0.1+12-Ubuntu-120.04)
OpenJDK 64-Bit Server VM (build 17.0.1+12-Ubuntu-120.04, mixed mode, sharing)If you see something like the above message, then everything is all
set and ready to go! If you see a different Java version after running
java -version in the Terminal, we need to tell Linux which
version of Java we want it to use by default. Open the Terminal and run
the following commands:
$ sudo update-alternatives --config java
There are 2 choices for the alternative java (providing /usr/bin/java).
Selection Path Priority Status
------------------------------------------------------------
* 0 /usr/lib/jvm/java-17-openjdk-amd64/bin/java 1711 auto mode
1 /usr/lib/jvm/java-16-openjdk-amd64/bin/java 1611 manual mode
2 /usr/lib/jvm/java-17-openjdk-amd64/bin/java 1711 manual mode
Press <enter> to keep the current choice[*], or type the selection number: Enter the number corresponding to Java 17, which in this case is
2 to manually set Java 17 as the chosen version. Rerun
java -version and you should now see a message about Java
17. Note: your interface might appear slightly different, but as
long as you see JDK 17 and are able to select it then you are all
set.
Open the Terminal application and run the following commands:
$ sudo yum check-update
$ sudo yum install java-17-openjdk
$ java -version
openjdk version "17.0.2" 2022-01-18
OpenJDK Runtime Environment 21.9 (build 17.0.2+8)
OpenJDK 64-Bit Server VM 21.9 (build 17.0.2+8, mixed mode, sharing)If you see something like the above message, then everything is all
set and ready to go! If you see a different Java version after running
java -version in the Terminal, we need to tell Linux which
version of Java we want it to use by default. Open the Terminal and run
the following commands:
$ sudo alternatives --config java
There are 2 programs which provide 'java'.
Selection Command
-----------------------------------------------
* 1 java-11-openjdk.x86_64 (/usr/lib/jvm/java-11-openjdk-11.0.12.0.7-4.fc35.x86_64/bin/java)
+ 2 java-17-openjdk.x86_64 (/usr/lib/jvm/java-17-openjdk-17.0.2.0.8-1.fc35.x86_64/bin/java)
Enter to keep the current selection[+], or type selection number: Enter the number corresponding to Java 17, which in this case is
2. Rerun java -version and you should now
see a message about Java 17. Note: your interface might appear
slightly different, but as long as you see JDK 17 and are able to select
it then you are all set.
If you do not have a computer that uses any of the above operating systems, such as a Chromebook, or do not have the ability to install software, such as a work or library computer, don’t worry! There is a web service that can be used to follow 95% of this book. The only issue is that, at the time of this writing, the service only goes up to Java 11 and does not yet support Java 17. Throughout this book we will notate the topics that are Java 17 specific and show how things were previously done in Java 11, which means you will be able to follow along and complete the project using Java 11 strategies.
The service is called replit and can be found at https://replit.com/. Make an account and create a Java repl, using the default settings. You must have the Main.java file, which is what the relp will run, but other files can be added to match those throughout this book. Note: whenever you see Java program with a main method in this book, you must write that code in the Main.java file or the repl will not be able to run your code. The shell panel can be used to run the jshell examples throughout the book as well.
Now that we have the Java language installed, it’s time to move on to the second step: installing a tool to write and run Java code! There are many such tools, and we will be using the software called IntelliJ. IntelliJ is an integrated developing environment, or IDE, for Java published by the company JetBrains. This means we can write, run, debug, test, and analyze our code all in one system! We will primarily be using the write and run functionality, but we will also occasionally use the debug feature. We will learn how to use IntelliJ in context as we move forward throughout the book, so this chapter only covers how to install the system.
IntelliJ comes in two versions: the Ultimate Edition and the Community Edition. The Ultimate Edition comes with extra features and support for several web and enterprise-level frameworks that are beyond the scope of this book and it also costs money. The Community Edition provides support for basic Java and is free, so this is the version you should download at https://www.jetbrains.com/idea/download/. The web page should automatically select the correct download option for your computer, but make sure to double-check both the operating system and, if you’re on a Mac, the correct chip type (follow the steps in the Mac Java installation section to figure out which chip type your Mac has).
To install IntelliJ on Windows, simply download the installer and follow the directions. The default settings will be fine for this book.
To install IntelliJ on Mac, simply download the image and follow the directions. The default settings will be fine for this book.
To install IntelliJ on Debian/Ubuntu- and Red Hat-based Linux distribution, download the tarball and open your terminal application. Note: your numbers might be different depending on the current version of IntelliJ at your time of reading, but the most important part is that you downloaded the Community Edition as shown by ideaC. Navigate to your Downloads folder and run the following command:
$ tar -xf ideaC-2021.3.2.tar.gzOnce the tarball has been unpacked, you will see a new folder with a name along the lines of idea-IC-213.6777.52. You can now move this folder to wherever you want to keep IntelliJ on your system. Once moved, open the file Install-Linux-tar.txt and follow the directions to finish installing IntelliJ.