Hello World in Java (Windows)

This guide explains how to configure a Java programming environment on Windows Windows logo , create and compile a Java program in IntelliJ, and run it from the command line.

You will need a 64-bit version of Windows 10 or 11 on Intel/AMD x64 hardware. (We also have an experimental installer for Windows ARM64.)

0. Install the Java Programming Environment

The installer configures OpenJDK 21, IntelliJ IDEA, OSS Edition 2026.2, and the course tools and libraries.

Sign in to the Windows account you will use for programming. The account must have administrator privileges.
Download the Windows installer.
- For Intel x64 and AMD x64, use lift-java-installer-x64.exe.
- For ARM64, use lift-java-installer-arm64.exe.
Double-click the downloaded installer. Enter your Windows password when prompted and accept the default options.

Warning

If you have previously customized IntelliJ, run the installer only if you want a clean reinstall. It replaces IntelliJ IDEA, OSS Edition and its associated user settings.
The installer also performs a clean reinstallation of Git Bash, which will overwrite any previous user settings, including .bashrc.
After installation, delete lift-java-installer-x64.exe or lift-java-installer-arm64.exe. You may also delete IntelliJ IDEA CE.exe, if present; it has been superseded by IntelliJ IDEA, OSS Edition.

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.

Download the project for your programming assignment to a convenient location (such as the Desktop).
[ sample project for COS 126 (Princeton) ]
- hello.zip
[ sample project for COS 226 (Princeton) ]
- hello.zip
[ sample project for Computer Science: Programming with a Purpose (Coursera) ]
- hello.zip
[ sample project for Algorithms, Part I or II (Coursera) ]
- hello.zip
To extract the ZIP file, right click it and select Extract All. 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.
To launch IntelliJ, click the Start button and type “IntelliJ IDEA, OSS Edition 2026.2”.
When you launch IntelliJ for the first time,
- It may display the JetBrains privacy policy. Scroll down and Accept.
- It may ask if you want to send anonymous usage statistics to JetBrains. Choose your preferred option.
- It will display the Welcome to IntelliJ IDEA screen.
To open a project from the Welcome to IntelliJ IDEA screen, click Open and select the project folder.

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 (Ctrl + 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.
When you are finished working, select File → Exit to exit IntelliJ. The next time you launch IntelliJ, your recent projects will appear in the Welcome to IntelliJ IDEA screen for easy access.

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.

To create a new Java program:
- Reopen IntelliJ and the project (if you closed it in the previous step).
- Select the project name in the left Project View sidebar. If you don't see the Project View sidebar, select LIFT → Project (Ctrl + 1) to toggle it on.
- Select LIFT → New Java Class. Enter HelloWorld as the Name and press Return.
In the main editor window, complete 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"); } }
As you type, IntelliJ highlights different syntax, inserts matching brackets, and indents new lines.
Select File → Save All (Ctrl + S) to save and, if necessary, reformat your code. IntelliJ also saves automatically before events such as as compiling, running, closing a project, or quitting.

3. Compile and Execute the Program (from IntelliJ)

Before Java can execute (or run) your program, it must compile the source code.

Select the program that you wish to compile and run in the Project View sidebar. The program should now appear in the main editor window.
To compile your program, select LIFT → Recompile 'HelloWorld.java' (Ctrl + B). If compilation succeeds, a confirmation appears in the status bar.

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.
To run your program, select LIFT → Run 'HelloWorld' with Arguments (Ctrl + E). Because the program takes no command-line arguments, click OK without entering any.

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 Execute 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.

Select LIFT → Terminal (Alt + 2).
This opens an embedded Git Bash terminal. You will see a command prompt that looks something like this:
```
~> Active code page: 65001
```
~/Desktop/hello is the current working directory; ~ denotes your home directory.
To compile your program, type the following javac command (highlighed in yellow below).
```
~> javac HelloWorld.java
~>
```
If HelloWorld.java is in the current directory and contains no errors, the javac command produces no output.
To run your program, type the following java command:
```
~> java HelloWorld
Hello, World
```
You 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.

Computer Science: An Interdisciplinary Approach (including COS 126 students). The program Barnsley.java uses our standard drawing and standard random libraries in stdlib.jar to draw a Barnsley fern.
- Download Barnsley.java and to move it to a project folder (such as hello). Then compile and run it with the following commands:
```
~> ls
Barnsley.java   COS 126.iml   HelloWorld.java   logo.png
~> javac-introcs Barnsley.java
~> java-introcs Barnsley 10000
```
When you run the program, the standard drawing window opens and generates the image one point at a time.

To get your command prompt back, close the standard drawing window.
Algorithms, 4th Edition (including COS 226 students). The program CollidingDisks.java uses classes from 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:
```
~> ls
CollidingDisks.java   COS 226.iml   WELCOME.txt   logo.png
~> javac-algs4 CollidingDisks.java
~> 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

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Installer FAQ

I installed IntelliJ and Java using lift-java-installer-x64.exe last semester or year. Should I run the installer again this semester?

Yes. This installer includes IntelliJ and Java 21. The old installer may have used an earlier version of IntelliJ or Java. Be sure to uninstall the old version before proceeding.

I wrecked some of my IntelliJ settings. Can I rerun the installer to restore the settings?

Yes. However, the proper way to reinstall software on Windows is to completely uninstall it and then to reinstall it. So, first, uninstall the software; then, run lift-java-installer-x64.exe.

How can I uninstall the software?

To uninstall everything, navigate to C:\Program Files\LIFT-CS and launch the uninstaller unins000.exe.
To uninstall only IntelliJ, navigate to C:\Program Files (x86)\JetBrains\IntelliJ IDEA, OSS Edition 2026.2\bin; right click the uninstaller Uninstall.exe; and select Run as administrator.

Can I run the installer using Run as administrator?

No. You must run the installer from an account in which you wish to program, and that account must have Administrator privileges. If you use Run as administrator, the installer will not know the original user’s identity (so it can’t copy files to the original user’s home directory).

The installer failed. How can I investigate why?

Check the installer logs at %TEMP%\LIFT-CS\ and %TEMP%\Setup Log YYYY-MM-DD #NNN.txt, where %TEMP% is typically C:\Users\<Username>\AppData\Local\Temp, YYYY-MM-DD is the current date, and NNN is an integer.

My machine is running Windows 8. Is that too old?

Yes. IntelliJ 2026.2 requires Windows 10 or 11.

How long will the installer take to complete installation?

After downloading, installation should take about two minutes. The progress bar will not move while it installs the IntelliJ component, so please be patient.

What does the lift-java-installer-x64.exe installer do?

In short, it installs and configures Java, IntelliJ, Git Bash, Xming, SpotBugs, PMD, Checkstyle, and our textbook libraries, along with accompanying command-line tools. Here is a more detailed list:

Installs Temurin OpenJDK 21.0.11 and adds it to the PATH.
Installs IntelliJ 2026.2 with customized user preferences.
Installs Git Bash 2.50.1 and adds it to the PATH.
Installs Xming 6.9.0.31.
Installs the following command-line tools for Java:
- The textbook libraries stdlib.jar and algs4.jar.
- Java wrapper scripts, including javac-algs4 and java-algs4.
- SpotBugs 4.8.4; our SpotBugs configuration file spotbugs.xml; and wrapper script spotbugs.
- PMD 6.34.0; our PMD configuration file pmd.xml; and wrapper script pmd.
- Checkstyle 10.26.1; various configuration files (checkstyle-cos126.xml, checkstyle-cos226.xml, checkstyle-coursera.xml, and checkstyle-suppressions.xml); custom checks checkstyle-lift.jar; and wrapper script checkstyle.

How is the software licensed?

All of the included software is licensed under various open-source licenses.

IntelliJ IDEA, OSS Edition is licensed under the Apache License, Version 2.0.
OpenJDK 21 is licensed under the GNU General Public License, version 2, with the Classpath Exception.
SpotBugs is licensed under the GNU Lesser Public License, Version 2.1.
Checkstyle is licensed under the GNU Lesser Public License, Version 2.1.

PMD is licensed under a BSD-style license.
Git Bash is licensed under the GNU General Public License, version 2.
Xming is licensed under the MIT X License.
stdlib.jar and algs4.jar are licensed under the GNU General Public License, Version 3.

What’s the SHA-256 checksum of lift-java-installer-x64.exe?

2461f3ef187aa3dfd1fb5de8f000265a50fdb83de28d6e7ee41dea435495da7e

How can I run the installer from the command line?

lift-java-installer-x64.exe accepts optional command-line arguments, which can be useful to system administrators.

Java FAQ

Can I use a different Java or version?

Yes. You may use any version of Java 11 or newer from either Oracle or OpenJDK. If you do, you may need to configure the Platform SDK and Project SDK manually in IntelliJ under File → Project Structure. We recommend using long-term support (LTS) versions: Java 11, Java 17, Java 21, and Java 25.

How can I check which version of Java is installed (and where it is installed)?

Type the following commands in the terminal:

~> javac -version
javac 21.0.11
~> 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)

~> which javac
c/Program Files/Eclipse Adoptium/jdk-21.0.11.10-hotspot/bin/javac

~> which java
c/Program Files/Eclipse Adoptium/jdk-21.0.11.10-hotspot/bin/java

With the default installation, javac and java should both report version 21.

IntelliJ FAQ

How does this customized version of IntelliJ different from the standard one?

IntelliJ is an industrial-strength integrated development environment (IDE), suitable for use by professional programmers. The installer configures your user preferences to make it more suitable for use by novice programmers:

Disables all built-in plugins except Terminal and JUnit. Installs the SpotBugs, Checkstyle-IDEA, Run-with-Arguments, Save-Actions, and Archive browser plugins.
Eliminates or reduces various pop-up elements (lightbulbs, code folding, breadcrumbs, gutter markers, notifications, parameter hints).
Simplifies menus and toolbars, hiding advanced options.
Disables live templates and postfix completion.
Adopts the Obsidian Black color scheme.
Configures Java automatically.
Adds a few keyboard shortcuts.

The course-specific project folders provide additional customizations:

Streamlines autocomplete to display only relevant libraries (such as java.lang, java.util, and algs4.jar).
Configures SpotBugs and Checkstyle with course-specific rules.
Provides course-specific libraries (such as algs4.jar).
Enables automatic formatting of code on save.
Enables automatic importing of Java libraries.

How can I manually configure the Platform SDK and Project SDK in IntelliJ?

The installer should configure the Platform SDK automatically. To configure it manually,

Navigate to File → Project Structure → Platform Settings → SDKs.
Click the + symbol (upper left) to add an SDK.
Select the JDK installation directory. A typical location for a JDK on Windows is C:\Program Files\Java\jdk21.0.11.
Use the shorthand name suggested by IntelliJ (e.g., 21 for version 21.0.11).

To manually configure the Project SDK,

Navigate to File → Project Structure → Project Settings → Project.
Choose the desired Project SDK from the drop-down list.
Be sure to use 21 as the Project language level, as our autograder currently supports only Java 21 features.

Where should I store my projects?

Store projects on a local drive (not a network drive, cloud-synced folder, or SMB share). Create one course folder with a separate subfolder for each assignment.

Are ther any special characters to avoid when naming IntelliJ projects or files?

Do not end the name of a project folder (or any enclosing directory) with an exclamation mark (!); doing so confuse IntelliJ and Checkstyle.

How can I create a new project in IntelliJ?

If you want to inherit all of the properties of an existing project,

Use Windows Explorer to copy the project folder, giving it your preferred name.
Delete any unwanted files.
Be sure to keep the .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.

What are the most important IntelliJ menu options to remember?

Here are the most important ones (and their shortcuts).

LIFT → New Java Class (Ctrl + N). Create a new Java class.
LIFT → Recompile (Ctrl + B). Compile the current program.
LIFT → Run with Arguments (Ctrl + E). Run the current program with command-line arguments.
File → Save All (Ctrl + S). Save (and reformat) all open files.
View → Tool Windows → Project (Alt + 1). Show/hide the Project View sidebar.
View → Tool Windows → Terminal (Alt + 2). Show/hide the Terminal window.

Can I use a version of IntelliJ that is newer than 2026.2?

Yes, though if it is 2026.3 (or above), you will need to migrate your user preferences.

How can I restore the original IntelliJ settings (instead of the custom novice-friendly ones)?

To restore the menus and toolbars: Settings → Appearances & Behavior → Menus and Toolbars → Restore All Defaults.
To restore all settings: File → Manage IDE Settings → Restore Default Settings.

Command-Line and Embedded Terminal FAQ

When I compile or run a program from the command line that uses one of the textbook libraries, I get an error that it cannot find the library. How can I fix this?

Make sure that you are using the appropriate wrapper script, such as javac-algs4 or java-algs4.

When I open the IntelliJ embedded terminal, IntelliJ either launches the wrong version of Bash (such as WSL Bash on MinGW Bash) or produces an error message (such as "couldn't create PTY error"). How can I fix this?

Navigate to File → Settings → Tools → Terminal → Shell path and replace bash with "C:\Program Files\Git\bin\bash.exe".

I get an error when I try to use run a wrapper script (such as javac-algs4 or java-introcs). How can I fix this?

IntelliJ is probably launching the wrong shell (such as Command Prompt, PowerShell, WSL Bash, or MinGW Bash). To reconfigure to use Git Bash, follow the instructions in the previous question.

International characters appear garbled in the terminal. What could cause this?

When you launch the terminal, you should see the message Activation code page: 65001, which configures the terminal to displays Unicode characters using UTF-8. If you don't see this message, you are probably using the wrong version of Bash (such as WSL Bash or MinGW Bash). To reconfigure to use Git Bash, follow the instructions in the previous question.

How should I configure Bash?

If you followed our instructions, our wrapper scripts (such as 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.

How do I break out of a program in an infinite loop?

Type Ctrl-C.

How do I specify EOF to signal that standard input is empty?

On macOS and Linux, press Enter, then Ctrl-D. On Windows, press Enter, Ctrl-Z, and then Enter, even in Git Bash.

How can I run SpotBugs, PMD, and Checkstyle from the command line?

The installer includes wrapper scripts to simplify this process.

To run SpotBugs 4.8.4, type the following command in the terminal:
```
~> spotbugs HelloWorld.class
Running spotbugs on HelloWorld.class:
```
The argument must be a list of .class files. Here is a list of bug descriptions.
To run PMD 6.34.0, type the following command in the terminal:
```
~> 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.

To run Checkstyle 10.26.1, type one of the following commands in the terminal, depending on whether you are COS 126, COS 226, or Coursera student:

~> checkstyle -cos126 HelloWorld.java
Running checkstyle on HelloWorld.java:

~> checkstyle -cos226 HelloWorld.java
Running checkstyle on HelloWorld.java:

~> 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.

Can I use the Command Prompt, PowerShell, or Windows Subsystem for Linux instead of Git Bash for Windows?

We strongly recommend Git Bash. For example, the commands javac-algs4 and checkstyle-algs4 will work only in Git Bash. If you want to use another shell, you’ll need to configure it yourself.

Which Linux-style commands are available in Git Bash for Windows?

Here are the Bash built-in commands and here are the external commands in C:\Program Files\Git\usr\bin.