This guide explains how to configure a Java programming environment
on macOS
,
create and compile a Java program in IntelliJ,
and run it from the command line.
This guide explains how to configure a Java programming environment
on macOS
,
create and compile a Java program in IntelliJ,
and run it from the command line.
You will need an Apple silicon Mac running macOS 15 (Sequoia) to macOS 26 (Tahoe).
| 0. Install the Java Programming Environment |
The installer configures
OpenJDK 21,
IntelliJ IDEA, OSS Edition 2026.2,
and the course tools and libraries.
Warning
If you have previously customized IntelliJ,
run the installer only if you want a clean reinstall.
It replaces IntelliJ IDEA OSS.app and
its associated user settings.
By default, it also replaces existing Bash configuration files,
including .bashrc.
To preserve these files, see the FAQ.
| 1. Open a Project in IntelliJ |
You will develop your Java programs in IntelliJ,
which organizes programs into projects.
In our context, each project corresponds to one programming assignment
and contains source files, data files, and course-specific settings.
[ sample project for COS 126 (Princeton) ]
[ sample project for COS 226 (Princeton) ]
[ sample project for Computer Science: Programming with a Purpose (Coursera) ]
[ sample project for Algorithms, Part I or II (Coursera) ]
If needed, double-click the ZIP file to extract it.
This creates a project folder with the
name of the corresponding programming assignment (such as hello).
You may delete the ZIP file.
Warning
Each project contains course-specific information. Be sure to download the project for your institution and course.
You should see an assignment logo (in the main editor window) and a list of
project files (in the Project View sidebar at left).
If you don't see the Project View sidebar,
select LIFT → Project (⌘1) to toggle it on.
Warning
Open the project folder, not an individual file Do not select New Project, which is intended for advanced programmers.
| 2. Create a Program in IntelliJ |
Now you are ready to write your first Java program.
IntelliJ provides syntax highlighting, bracket matching,
automatic indentation and formatting, automatic imports, variable renaming,
and continuous code inspection.
HelloWorld.java so that
it matches the code below.
Note that IntelliJ generates the gray boilerplate code automatically.
A missing semicolon will prevent the program from compiling.
public class HelloWorld { // prints "Hello, World" public static void main(String[] args) { System.out.println("Hello, World"); } }
| 3. Compile and Run the Program (from IntelliJ) |
Before Java can execute (or run) your program,
it must compile the source code.
If it fails, the Recompile panel opens at the bottom and lists any errors or warnings. Check your program carefully for typos, using the error messages as a guide.
You should see the output of the program (highligted in white below), along with a message that the program finished normally (with exit code 0).
Tip
Use the LIFT menu to compile and run your program from IntelliJ. The Build and Run menus support additional options for advanced programmers.
Before using the LIFT menu, click inside the editor window to make it active.
| 4. Compile and Run the Program (from the command line) |
The command line provides a simple and powerful way to control programs
using command-line arguments, file redirection, and piping.
IntelliJ includes an embedded terminal
for convenient access.
~/Desktop/hello>
~/Desktop/hello is the current working directory;
~ denotes your home directory.
javac command
(highlighed in yellow below).
~/Desktop/hello> javac HelloWorld.java ~/Desktop/hello>If
HelloWorld.java is in the current directory
and contains no errors,
the javac command produces no output.
java command:
~/Desktop/hello> java HelloWorld Hello, WorldYou should see the output of your program beneath the line on which you typed the command.
Tip
For routine work, compile compile in IntelliJ, which identifies errors by line, and run from the command line, which makes command-line arguments and file redirection easier.
| 5. Textbook Libraries (from the command line) |
To make our textbook libraries accessible to Java from the command line,
you will use our wrapper scripts.
stdlib.jar to draw a
Barnsley fern.
hello).
Then compile and run it with the following commands:
~/Desktop/hello> ls Barnsley.java COS 126.iml HelloWorld.java logo.png ~/Desktop/hello> javac-introcs Barnsley.java ~/Desktop/hello> java-introcs Barnsley 10000
To get your command prompt back, close the standard drawing window.
algs4.jar
to simulate the motion of n disks subject to the laws
of elastic collision.
Download
CollidingDisks.java
and move it to a project folder (such as hello).
Then compile and run it by typing the following commands:
~/Desktop/hello> ls CollidingDisks.java COS 226.iml WELCOME.txt logo.png ~/Desktop/hello> javac-algs4 CollidingDisks.java ~/Desktop/hello> java-algs4 CollidingDisks 20
When you run the the program, the standard drawing window opens and animates 20 colliding disks.
To get your command prompt back, close the standard drawing window.
| Frequently Asked Questions |
javac-introcs and
javac-algs4
.bashrc,
.bash_profile, and
.inputrc files.
We generally recommend a full installation. A custom installation can be useful if you
already have a specialized
.bashrc file.
It might also speed things up
if you need to reinstall, say IntelliJ IDEA, OSS Edition 2026.2, but not Java.
.bashrc file. How can I revert to the original version?
.bashrc.20210706-191748.
Rename or copy the most recent backup to .bashrc.
/var/log/lift.log.
stdlib.jar and
algs4.jar.
javac-algs4 and
java-algs4.
.bashrc,
.bash_profile, and
.inputrc files.
spotbugs.xml;
and wrapper script spotbugs.
pmd.xml;
and wrapper script pmd.
checkstyle-cos126.xml,
checkstyle-cos226.xml,
checkstyle-coursera.xml, and
checkstyle-suppressions.xml);
custom checks checkstyle-lift.jar;
and wrapper script checkstyle.
6feadf08beba0de0135840e8c768f9157883f6c2635618931d48d62beca81984.
sudo installer -verbose -pkg lift-java-arm64.pkg -target /
/Library/Java/JavaVirtualMachines/temurin-21.jdk/
/Applications/IntelliJ IDEA OSS.app
~/Library/Application Support/JetBrains/IdeaIC2026.2/
~/Library/Caches/JetBrains/IdeaIC2026.2/
~/Library/Logs/JetBrains/IdeaIC2026.2/
/usr/local/lift/
/usr/local/bin/javac-{algs4,introcs}
/usr/local/bin/java-{algs4,introcs}
/usr/local/bin/jshell-{algs4,introcs}
/usr/local/bin/spotbugs
/usr/local/bin/pmd
/usr/local/bin/checkstyle
~/Desktop/hello> javac -version javac 21.0.11 ~/Desktop/hello> java -version openjdk version "21.0.11" 2026-04-21 LTS OpenJDK Runtime Environment Temurin-21.0.11+10-LTS (build 21.0.11+10-LTS) OpenJDK 64-Bit Server VM Temurin-21.0.11+10-LTS (build 21.0.11+10-LTS, mixed mode, sharing) ~/Desktop/hello> /usr/libexec/java_home /Library/Java/JavaVirtualMachines/temurin-21.jdk/Contents/HomeWith the default installation,
javac and java
should both report version 21.
The course-specific project folders provide additional customizations:
java.lang,
java.util, and algs4.jar).
algs4.jar).
/Library/Java/JavaVirtualMachines/temurin-21.jdk/Contents/Home.
To manually configure the Project SDK,
!);
doing so confuse IntelliJ and Checkstyle.
.iml file (which defines the project),
the .idea subdirectory (which contains
the IntelliJ course preferences), and
the .lift subdirectory (which contains the course
libraries).
To create a new project from scratch, you can use the New Project option from the Welcome screen. But, we do not recommend this approach for novice programmers.
javac-algs4
or java-algs4.
javac-algs4 and
java-algs4)
should already be available.
The installer configures Bash by copying
.bashrc,
.bash_profile, and
.inputrc.
If you accepted the default installation options, no additional configuration is required.
Ctrl-C.
Enter, then Ctrl-D.
On Windows, press Enter, Ctrl-Z,
and then Enter, even in Git Bash.
~/Desktop/hello> spotbugs HelloWorld.class Running spotbugs on HelloWorld.class:The argument must be a list of
.class files.
Here is a list of
bug descriptions.
~/Desktop/hello> pmd HelloWorld.java Running pmd on HelloWorld.java:The argument must be either a single
.java file or
a directory containing one or more .java files.
Here is a list of
bug patterns.
~/Desktop/hello> checkstyle -cos126 HelloWorld.java Running checkstyle on HelloWorld.java: ~/Desktop/hello> checkstyle -cos226 HelloWorld.java Running checkstyle on HelloWorld.java: ~/Desktop/hello> checkstyle -coursera HelloWorld.java Running checkstyle on HelloWorld.java:The argument must be a list of
.java files.
Here is a list of
available checks.
zsh
to bash?
zsh as the default shell.
To use bash instead,
run the following command in Terminal and
enter your macOS password:
~/Desktop/hello> chsh -s /bin/bashFinally, close the Terminal application and reopen it. Note that the embedded terminal within IntelliJ is configured to use
bash regardless of
the default shell.
javac, I get an "error while writing"
message. How can I fix this?
bash as a safe program.