In this project, you will learn to use some of the “team” features of your preferred IDE (Eclipse, Apache NetBeans, or IntelliJ IDEA). We will use the “Git” source code control system to allow all members of the class to work on the same project at the same time, and then to merge in your changes. This is a “real-world” way of working on code; few developers work on real projects by themselves. (And even then, version control is often useful and used.)
The project is a very simple one.
The source file
SayHello.java has a
you need to edit.
Add a statement to
main to greet the class
by displaying a unique string (so your contribution differs from
other students'), which should include your name.
(You are free to add additional output if you desire,
such as a quote or joke.)
The purpose is simply to learn to use Git, which takes time and
lots of practice.
You can try using various IDEs, and make multiple
changes if you want.
For this project, every student must individually commit their change(s)and submit this assignment.
I have created a Git repository you can access from
This repository contains the initial version of
.gitignore file, and a bunch of other files needed
for a Maven project.
(There are also some Eclipse IDE and IntelliJ IDEA project files
in there, to make importing into those IDEs easier.)
The initial version has a greeting from the instructor you can use
as a model for your own additions.
(While it is okay to be a little creative, say by adding a joke or quote,
just don't go overboard and add more than a few lines!)
The URL of the repo is shown below, in the step-by-step
directions for each IDE.
You can also view the project's website
(generated by Maven from the initial version).
Following the directions below, you will create a GitHub account
for yourself, then clone the project's repo.
(IDEs generally require a local repo to work with as well.)
When you are done making a set of changes (for this project you only
need to add two lines to
main) to your local copy, you must
commit your changes.
That updates the local (on your PC) repository.
Next, you push your changes to the class' GitHub repo.
During this step you may discover another student has committed some
changes after you had checked out the project.
If so, you will need to merge your changes into the new version.
Or you can update your local copy of the project, over-writing
your files with the latest ones from the repository, and make your change
In either case, you must commit again, and then retry the push.
In the real world, you might not push changes directly to the master branch. Instead, you might make your change in a branch, then make a pull request for the project's team to review, comment on, revise, and hopefully, approve. The project leader would then pull in your branch (if it was in a different repo) and merge it into master.
See Pull Requests and Patches for more information.
You can perform other Git related operations with your IDE. It is expected that students will explore some of these operations. Eclipse assumes you may have multiple projects per repo, and thus creates a project top-level folder within the top (root) of the repo. NetBeans and IntelliJ IDEA don't do that by default, but they are perfectly happy either way, so I set up the GitHub class repo using the Eclipse conventions.
Another issue is that Eclipse doesn't easily import non-Eclipse projects with existing sources. It can be done, but it was easier to create the default Eclipse project files and add them to the repo. They should be ignored by NetBeans, and it shouldn't be modifiable by Git; the repo was set to ignore changes to those files.
You can read about using these features with your IDE using the built-in help system you have learned to use in a previous project. For more information visit the Git Home, especially the Git book online, and the other resources found on our class web page.
If you accidentally corrupt the class repo, you should notify your instructor as soon as possible.
Using your preferred IDE, complete the steps shown below for your IDE to setup a Git project. Then edit the shared Java program, test it, commit your change(s), and finally, push your changes back to the class repository (merging if necessary).
The first step is to make sure your IDE includes the latest Git plug-ins. It almost surely includes Git support by default but if not, see your IDE's documentation to see how to add plug-ins. (You can add some others if you wish, but until you are comfortable with your basic IDE features, I suggest you resist the temptation to install much extra.) You should also check for IDE updates, and install any found.
Next you need to create an account on GitHub.com. This is easy, fast, and free. When you have completed this step, you can create your own repositories there for practice. I strongly suggest you create one (or more) and practice using them with your preferred IDE before attempting any changes to the project's repo! (When done, you can delete any of your GitHub repos from their “Settings” screen.)
You must send an email containing your GitHub account name to your instructor. Only those listed as collaborators on GitHub.com can push changes to the COP-2805C-2019 repo there, and I need to add your account name to the list. Once you are added by me, you will receive an email message from GitHub with an “invitation” to collaborate; you need to accept that before you are a collaborator.
There are Windows GUI and command line tools for working with Git and/or GitHub. They are not full IDEs however; you view your repos, create new ones, and with some of these tools, add files or commit new versions of files. As the Git plug-ins for Eclipse and NetBeans includes a full version of Git, you don't need any other tool. (That is, this step is optional). Still, it is handy to be able to run various Git commands outside of an IDE, especially when trying to learn.
I would suggest installing “Git for Windows” from
Git for Windows includes a sub-set of the command line Linux tools, just
the ones you would need to work with Git at the command line.
(It also includes a Git GUI, but it doesn't do much.)
Windows 10 includes Linux, which includes Git.
Installing Git for Windows is probably your easiest choice.
I recommend configuring it (during the install) to allow you to run
git from a DOS command line.
Configure the other choices as you wish, but sticking to the defaults
is generally safest.
After completing the IDE-specific steps below, don't forget to continue with the remaining steps of the project.
user.name” with your full name, and “
user.email” with a working email address (such as your HCC Hawkmail address). This information will be automatically included with every commit.
If the email address you used is unknown to GitHub, your commits will not be linked to your GitHub account name! This is because GitHub accepts your commits if you know a username and password (or use an appropriate SSH key), but labels commit objects by your email address and not by username. You can list several email addresses in your GitHub account and then your commits will be recognized from any of them. Follow these directions to add additional email addresses to your GitHub account.
From Preferences→Team→Git, you can set a default location
for all your Git repos.
From Preferences→General→Workspace: Set the default text file encoding to UTF-8.
It's not required for our project, but the “Package Explorer”
hides many files by default.
In particular, it hides the “
To fix that, click on the tiny downward-pointing triangle on the right of
the Package Explorer tab bar, and click on “Filters and Customization”.
Now un-check “
To re-hide the Eclipse project files, select “Name filter
patterns” at the top, and enter
.classpath, .project, .git, JRE*”
(without the quotes) in the box.
Hide other files if you wish, or hide nothing at all — it's your
0.15.1”.) Click the Add button, then the Apply and Close button.
git” and not your GitHub name.
If all is well, you have cloned that Git repo locally too.
Display README files in project view Git Toolbar
user.name” with your full name, and “
user.email” with a working email address (such as your HCC Hawkmail address). This information will be automatically included with every commit. The resulting
.gitconfigfile (in your HOME directory) should then look something like this (the file may have additional entries too):
[user] name = Hymie Piffl email = email@example.com
(Of course, you need to use your actual name and email address.)
If the email address you used is unknown to GitHub, your commits will not be linked to your GitHub account name! This is because GitHub accepts your commits if you know a username and password (or use an appropriate SSH key), but Git labels commit objects by your email address. You can list several email addresses in your GitHub account and then your commits will be recognized from any of them. Follow these directions to add additional email addresses to your GitHub account.
Set the default file encoding to UTF-8. You can change the file encoding for any one project by right-clicking on the project name (in the Projects tab), selecting Properties, and changing it there. To change the default for all new projects, follow these directions from StackOverflow.com.
firstname.lastname@example.org:profwpollock/COP-2805C-2019.git” should be changed to “
ssh://email@example.com/profwpollock/COP-2805C-2019.git”. Next, browse to locate your private key file, created outside of NetBeans. (Or, as I keep saying, just use HTTPS and a password.) Make sure the URI is correct; if using SSH, make sure the Username field is filled with “
Unlike Eclipse, NetBeans integrates Maven. Right-click on the project, and see the menu options (Build, Clean and Build, Clean, etc). Each call the corresponding Maven command when clicked. Additionally, you can custom goals to the menu.
Like NetBeans, IntelliJ IDEA can use SSH but not manage your SSH keys. However, the initial setup is more complex. See below for details.
In the project window, open up src/main java/mypkg/SayHello. If you try to run or test your project, you may see an error message about a non-existing SDK (Software Development Kit; not all IDEA projects are Java projects). I named the JDK to use as "JDK 11", so unless you did the same you will see the error message. Just select the correct JDK that you have installed. If your installed JDK doesn't appear in the list of known SDKs, click the plus-sign to add your JDK to the list. (The default name is just the version number. I like to change that to JDK version, for example “JDK 11”.) When you click OK, you are taken back to the setup window. Select your newly added JDK and click OK.
You should be able to run the main or the test by selecting an appropriate Run configuration, or from the Maven menu (double-click Install, then exec:java).
src→main→java→mypkgpackage (folder) to see the “
SayHello.javaand add your code. Make sure the code will compile and run, and displays your greeting along with the other greetings from your fellow classmates. Save your work.
Commit your changes to save your work to your local repository.
Enter a comment for your commit (called either a log message or
commit message) describing your update.
(To receive full credit, you must include an appropriate
Before committing, make sure your commit includes
and does not include any other files.
Not all IDEs ignore the configuration files, even if listed
.gitignore file, so double-check before making the
If using IntelliJ IDEA, it is at this point you need to enter your email address and name. This is because the other IDEs store a single name and email in their settings, and automatically use that. IDEA allows multiple people to work on the same computer and commit, so it keeps a drop-down list of previous committers and there is no prior configuration needed. Simply add your name and email in the “Author:” box in the commit dialog. The format should match this example:
Hymie Piffl <firstname.lastname@example.org>
Either click in the box and type control+space to see the list, or just start typing the name and it will auto-fill the box.
Note that only the Master branch of the class' GitHub repo will be graded. So if you did your change in a branch, be sure to merge your commit into your master branch before proceeding. When finished with this project, you should close it. (This should help prevent “accidents”!)
With Eclipse, right-click on your project and select
“Show in History”.
The Master branch's HEAD should be the commit with your change in it.
Right-click on that commit in the history, and select
File to save your patch (a pull request) in a file;
the default name of the file defaults to the first line of your commit
message, but you can change that if you wish.
Now you can choose a patch file format. Eclipse can only apply
patches made in the “Eclipse workspace” format, but for
this project use the standard “Git (e-mail header)”
With NetBeans, with the
showing, click on Team→Show History.
The Master branch's HEAD should be the commit with your change in it.
Click on the box with the plus-sign, to expand your choices.
Now click on “
Export Commit...” to make a
patch file (a pull request).
Save it someplace (say, on your desktop) with a descriptive name, something
like “hpiffl pull request”.
With IntelliJ IDEA, click the VCS→Create patch... menu item. Add a commit message and save the patch as a file (the commit message is used to name the file).
You should examine your patch file in a text editor. See if you can understand the format; someday you may wish to tweak one of these files before sending off the email. Your IDE can show it to you with color and syntax highlights; that may help you understand the format.
(View a Sample Patch File.)
If you opened the project a while ago, others may have made changes since you downloaded the files. In this case, Git won't be able to automatically merge the changes since both changes were to the same file. (The error message will say something about fast-forward failed.) You must Fetch the new commit(s) into your local repo, then Merge your changes with those (locally). All three IDEs have nice merging tools; they work best with a wide-screen monitor. You should definitely review your IDE's tutorial for Git merging before trying this out! After reconciling the differences (and testing to make sure the code still runs), you complete the merge with a commit. Then you can push that merge commit to GitHub without problems.
You should explore some of the other items on the “Team” or VCS menu. You are encouraged to create your own projects locally and on GitHub, create branches, and play with them. (A simple project with just a ReadMe.md file can be used to practice merging: make a local project, edit the file directly on GitHub, then make a change locally and try to push it.)
Try creating your own repo on GitHub, it's easy.
I suggest you check the box to create an initial
Without at least one commit in it, it isn't possible to clone a repo.
(You can push to an empty repo, however.)
Adding this file means you can clone the repo easily using any IDE
or even the command line.
From the repo's settings page, you can delete a repo when you are done with it (or after you messed it up badly and want just to start over). You can create as many repos as you like on GitHub. They are all public unless you pay money for a private repo. (That means anyone can clone and view it; but only you and those you add as collaborators can push changes to it.)
Working with a local repo is easier than working with a remote one. You can create a new project and share it using your IDE's Team menus. This will create a local Git repo, for your project only. With this, it is easy to practice making many commits, checking out old ones, creating branches, and merging branches. Since you only are using a private, local repo, there is no push or fetch (pull) to worry about.
If you mess up working with your IDE and want to start over, that is easy too. Simply delete the project (including all files) from the IDE. Next, find the Git repo created on your computer for that project; it is separate from the IDE's project folder (usually). Then delete that too. Now you can import the Git repo from GitHub again, and create a new project.
Please spend some time exploring the Git resources from our class web site. They can really help, and I promise Git has many more features than you will use on this simple project. Try not to forget the purpose of this project: to spend time learning Git.
NetBeans and IntelliJ IDEA can use
SSH keys, but can't generate them.
You will need additional software to create a pair of keys, each in a
You then configure your IDE with the names of the files
containing your keys.
You can use the keys generated by Eclipse or by the
tool that comes with Cygwin
or Git for Windows.
Launch the Bash (command line) window, and follow the directions from
Git-SCM.com/.../Generating-Your-SSH-Public-Key or from
Eclipse can generate and use SSH keys:
wpollock@home” or “
wpollock-ssh-key”), and also save the public key in a similarly named file (in this case, “
wpollock-ssh-key.pub”). You don't have to password protect your private key, but keep in mind anyone or any malware with access to your computer can use that key! So best practice is to password protect your private keys with good passwords. Make a note of the files location. Make an off-line backup of the files as well.
Creating Keys from the Command Line:
Open Git for Windows command line window (or CygWin or the Linux Subsystem for
Windows 10, or a terminal window on a Mac).
The prompt for the window may vary, I will show it as
At the prompt, type the following:
$ ssh-keygen -t rsa -C "email@example.com"
This will generate an RSA key pair named
id_rsa (the private key file) and
(the public key file).
Note that not having a password on your key sounds convenient, but it
is in fact dangerous!
So don't do that.
Once you have your key pair, you must upload the public key to GitHub.com so you can use it. Follow the directions at help.GitHub.com to upload your public key. (Don't forget to make backups of your key files!)
• Keys cannot be recovered if lost.
Make sure you have a good backup copy (or two)!
• Use of your private key may have legal implications. Either protect your private key with a strong password, or don't use that key for any other purpose.
To test your key, follow the directions at help.github.com/articles/testing-your-ssh-connection.
If you have trouble using keys, remember you can use
HTTPS protocol instead (with a password).
You can also ask your instructor for help.
If using IntelliJ IDEA, you need to use some external (“native”)
SSH client, and not the internal one that comes with IDEA.
This is because you cannot configure IDEA with the name of a key to use, or
even to have multiple keys.
(It only uses
id_rsa as the private key file name.)
So you should configure IDEA to use the native SSH
.sshor something similar, in your home directory.
config”. To keep this simple for now, just add a single key for yourself, for GitHub. A sample might look like this:
# Default key used for GitHub: Host github.com User git HostName github.com IdentityFile ~/.ssh/id_rsa
Email a copy of your patch file (or pull request), by copy and paste, which
SayHello.java Java source code additions.
(No credit if your changes aren't found on the master branch of the class'
GitHub repo, or if you don't use an IDE to make the changes.)
You can send as email to
If email is a problem for some reason, you can submit the patch as an
attachment, or you may turn in a hard-copy.
In this case the pages should be readable, dated, and stapled together.
Your name should appear on the first page.