You have been provided a VirtualBox image of Ubuntu 18.04 containing the recommended development environment for this course. It has pre-configured installations of Java 8, Gradle, Error Prone, and Emacs. Scripts have been provided to make using these tools a little easier for the Linux novice. Other configurations are possible on other operating systems using other editors, though you must use Gradle and ErrorProne.
The following will walk you through working with two small test projects on the VM.
Modifying an Existing Test Program
Start your VM using VirtualBox and log in using the user and password csc241.
If you are not proficient at the Linux terminal, you should now complete the tutorial at LinuxCommand.org
Open a terminal (bottom icon on the left bar) and change to the Projects directory.
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# Enter the Projects directory cd Projects |
Use the command ls to list the directory contents. You should notice four files. One (colored in blue) is a folder for a test project. The other three are scripts which we will use to make our lives a bit easier in a bit. Change into the TestProject directory.
Gradle project directories contain a build.gradle file which is used to configure the build. Print the contents of this file to your console by typing
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cat build.gradle |
You should see something like the following:
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plugins { id "net.ltgt.errorprone" version "0.0.16" } repositories { mavenCentral() } apply plugin: 'java' |
This says that the project will be built using java and the ErrorProne plugin. It also sets up a repository for where to download the plugin and any dependencies specified.
Gradle forces all of your java files to be in the src/main/java subdirectory. Use ls to see what’s in this directory by typing the following:
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ls src/main/java |
You should see only one java file – Test.java. Use cat to print out the contents of the file to your terminal.
As you can see, this file isn’t very interesting. It only prints out the text “Hi there” and quits.
We can build the project by using Gradle. In the ~/Projects/TestProject directory, type gradle build. You should see that the build was successful.
Gradle places the output of our file in the build/classes/java/main subdirectory. Change into that directory and list the contents of the directory using ls. You should see your Test.class file. Run it.
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csc241@csc241-VirtualBox:~/Projects/TestProject$ gradle build > Task :compileJava This build is using the default Error Prone dependencies, which always uses the latest release of Error Prone, and might break your build at any time. Configure the Error Prone dependencies explicitly to silence this warning. BUILD SUCCESSFUL in 2s 2 actionable tasks: 1 executed, 1 up-to-date csc241@csc241-VirtualBox:~/Projects/TestProject$ cd build/classes/java/main/ csc241@csc241-VirtualBox:~/Projects/TestProject/build/classes/java/main$ ls Test.class csc241@csc241-VirtualBox:~/Projects/TestProject/build/classes/java/main$ java Test Hi there |
Congratulations! You’ve built your first project using Gradle and ErrorProne!
Now lets edit our java file so we can see what happens when we make mistakes ErrorProne is designed to catch.
First, let’s open Emacs. Click the Emacs icon on the left bar to open it. Emacs is a programmable text editor – every part of it can be modified through plugins and a little code of your own. I’ve configured this installation with a few changes to make using it more pleasant.
If you are not proficient with Emacs you should now work through enough of the Emacs tutorial until you feel comfortable. You can safely ignore the warnings about M-x being rebound which the tutorial mentions, as the changes didn’t change its function. You may also wish to watch a video such as this one to get you started, and perhaps have a copy of the Emacs reference card on hand.
Using what you learned from those tutorials, open the Test.java file and modify it to contain the following:
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public class Test { public static void main(String... args){ if(true == true) { System.out.println("Hi there"); } } } |
Save the file. Now, return to your ~\Projects\TestProject directory and build the project. You should receive an error generated by ErrorProne. Java would say this file compiles, but ErrorProne is more strict! It tries to stop you from making silly mistakes.
Working with a New Project
Since all Gradle projects we will use have the same structure, one strategy is just to copy an existing project and modify it. A little better than this is a script which generates the appropriate files and directories.
Remember in your ~/Projects directory there were three scripts. Use cat to see the contents of initproj.sh. This bash script creates a project directory, writes the contents of the build.gradle file, and makes the src/main/java directories for us. Execute the script to make a new project called TestProject2.
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csc241@csc241-VirtualBox:~/Projects$ ./initproj.sh TestProject2 csc241@csc241-VirtualBox:~/Projects$ ls buildproj.sh initproj.sh runproj.sh TestProject TestProject2 |
You can see there is now a directory for this project. Make yourself a .java file in the appropriate place in TestProject2 for a program which uses a for loop to print the following:
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* ** *** **** ***** |
You could now use gradle build to build the project, and execute it by entering the /build/classes/java/main directory and executing it using the java command. I have also included two more scripts – buildproj.sh and runproj.sh. These build the given project and run it.
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csc241@csc241-VirtualBox:~/Projects$ ./buildproj.sh TestProject2 > Task :compileJava UP-TO-DATE This build is using the default Error Prone dependencies, which always uses the latest release of Error Prone, and might break your build at any time. Configure the Error Prone dependencies explicitly to silence this warning. BUILD SUCCESSFUL in 0s 2 actionable tasks: 2 up-to-date csc241@csc241-VirtualBox:~/Projects$ ./runproj.sh TestProject2 Triangle * ** *** **** ***** |
Examine the scripts to see how they work (hint: they aren’t much different than what we’ve been doing!)
You should now be ready to get started with the coursework! Remember to use these tools on all of the assignments!