Running Java in the command-line

I imagine that a lot of folks are compiling and running their Java code in the command-line for the first time for this assignment. This document is meant to help detail bits of that process that are useful to building the pa1.sh and setup.sh files to make sure your code is compiling and running properly for PA1 and beyond.

Running Java from the command-line

The standard way to run Java code in the command-line is, as one might expect, with the java command. What it always wants passed in is the name of the main class to run. If you’re running it from a directory that doesn’t contain all of your compiled .class files, it will also want a classpath, which tells you where those classes are! This is specified by the -cp option. So the standard call to java for us will look like

java -cp [PATH TO .CLASS FILES] [NAME OF MAIN CLASS]

where you substitute for the things in brackets. Given the structure I’ve given you in the Java project, pa1_template.pa1 is the name of the package/class our code is in, so we have to find the path where the pa1_template folder resides.

This is the line that should be in your pa1.sh file if you’re using Java!

Compiling Java Code

Your typical method for compiling Java code is probably either (1) just hitting compile & run in VSCode or (2) Using Gradle Build. The way things are set-up in VSCode, these may result in different locations where your code ends up! By default, running gradle build will put things in the java/build/classes/main/ folder, and VSCode places it in java/bin/main/