Definition
This is the page to follow during our first class meeting. It is a checklist, not a manual. Every step links to the full instructions on Development Environment Setup, which is the page to read at home and the one to come back to later.
Toolkit
What you need: a laptop and about 30 minutes. Nothing needs to be installed in advance.Pair with a neighbor and do this again tonight.
Install (Steps 1–4)
These four are the standard install, written up in full on the setup page. Do them in order.
Step 1 · IntelliJ IDEA
Download the free Community Edition and run the installer.
Assignment
✅ Checkpoint
IntelliJ opens to the Welcome to IntelliJ IDEA screen.
Step 2 · A JDK
Don’t install Java separately, IntelliJ fetches it. New Project → JDK dropdown →
Download JDK... → latest LTS (which shoud be 25), vendor Eclipse Temurin. Close the project afterwards; we only
came for the JDK.
Assignment
✅ Checkpoint
The JDK dropdown shows a version number instead of being empty.
Step 3 · Git
Install the Git tools, then open a new terminal and run git --version.
Careful
Windows students: keep Git Bash checked during installation. It’s on by default and easy to click past, but you’ll use it as your terminal all semester.
Assignment
✅ Checkpoint
You see a version number like
git version 2.43.0. “Command not found”? Close that terminal and open a brand new one — a fresh terminal is needed to pick up a new install.
Step 4 · GitHub account and token
Sign up at github.com if you haven’t, then create a Personal Access Token. Git no longer accepts your account password from the terminal.
Careful
Set the token to never expire, check all the permission boxes, and copy it somewhere safe immediately — GitHub shows it exactly once.
Assignment
✅ Checkpoint
You have a token saved somewhere you can find it in ten minutes.
Step 5 · Register on PostCommit
All assignments in this course are distributed and collected through PostCommit.
- Go to lmu.postcommit.ai and sign in with your LMU credentials. There is nothing to register for — I have already put you on the roster.
- You should land on a dashboard showing CMSI 2120.
- On that dashboard, complete the Connect GitHub to-do item, using the GitHub account from Step 4. Do not skip this -- without it you cannot open any assignment repository.
Debug
If you can’t find this course listed, tell me right now — that’s a roster problem on my end, not something you can fix from your laptop.
✅ Checkpoint
You see CMSI 2120 on your dashboard, and Connect GitHub is no longer in your to-do list.
Step 6 · Get Classwork 1 and open it
Assignment
-
Open Classwork 1 in PostCommit and click Accept. A private repository is created for you.
-
Click Open repository, then use GitHub’s green Code button to copy the HTTPS address.
-
In a terminal, move to wherever you want your coursework to live and clone it:
cd ~/ # or wherever you keep your projects git clone <paste-your-repo-address-here> -
Open it in IntelliJ with File > Open…
Careful
Select the folder that has
srcinside it. Not the folder above it, and not a single.javafile. This is far and away the most common reason a project looks empty, and it costs people the whole class block. When IntelliJ asks, click Trust Project.
When Git asks for a password, paste the token from Step 4. Nothing will appear as you paste — terminals hide passwords. Paste and press Enter.
✅ Checkpoint
The left-hand project panel shows a
srcfolder, andRunMe.javaopens with colored syntax — not plain black text, and no red underlines everywhere.
Step 7 · Run it
This is the whole point of today: proving your laptop can compile and run Java.
- Open
src/RunMe.java. - Click the green ▶ arrow in the gutter next to the class name.
- Choose Run ‘RunMe.main()’.
✅ Checkpoint
A Run panel opens at the bottom with a message printed in it, ending in
Process finished with exit code 0.
If you got that message, your environment works and you’re done with setup. Finish the README questions in Classwork 1, then:
git add -A
git commit -m "Answered README questions"
git pushToolkit
That
pushis what actually submits. Nothing counts as submitted until it’s pushed. The full clone/commit/push walkthrough lives in the PostCommit Tutorial.
Troubleshooting
Find your symptom. If the fix doesn’t work in two minutes, put your hand up — don’t burn the rest of class on it.
| What you’re seeing | What’s wrong | Fix |
|---|---|---|
| Project panel looks empty; no folder icons; red underlines everywhere | You opened the wrong folder level | File > Open... again, this time the folder that contains src. Still wrong? Right-click src → Mark Directory as > Sources Root |
| “No SDK” / the JDK dropdown is empty | No JDK attached to the project | File > Project Structure > Project, SDK field, Download JDK..., latest LTS, Eclipse Temurin |
git: command not found | Git isn’t installed, or your terminal predates the install | Close the terminal, open a new one. Windows: use Git Bash, not Command Prompt |
| Git asks for a password and rejects yours | GitHub no longer accepts account passwords | Paste your Personal Access Token from Step 4 instead |
| “I can’t find my file” | You’re browsing out/ | Your code lives in src/. out/ holds compiled output — ignore it entirely |
Red squiggles under @Test or import org.junit | JUnit isn’t on the classpath | Shouldn’t happen — our skeletons ship it preconfigured. Put your hand up, I want to see this one |
Remark
Nobody needs
javacworking at the terminal today. If that’s what’s broken on your machine, ignore it completely and open IntelliJ — this course never asks you to compile from the command line.
Assignment
After today
- Development Environment Setup — the full install reference, plus optional extras like command-line Java
- PostCommit Tutorial — cloning, committing, and submitting in more detail
- Java Style Guide — worth a read before the first homework
Debug
Setup is mandated by lecture L1-2. If you couldn’t finish today, come to office hours or catch me after class — do not let this ride until the first homework is due.