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This page is a guide to some aspects of configuring and using the Universal Algebra Calculator (UACalc). The main web site for UACalc is

Most of the instructions here are aimed at Linux users. If you use another operating system, feel free to use these notes as a guide.

Table of Contents

UACalc at the command line

Launching the UACalc GUI

The standard way to use the UACalc is through its graphical user interface. This requires Java. There are many ways to get the Java Runtime Environment working on a Linux machine, but here we describe how to install the full Oracle Java Development Kit (JDK). This is a reasonable option, especially if you plan to venture beyond the GUI, and write some Java or Jython or Scala programs that call UACalc Java packages.

Install Java

Here is one way to install Java on Ubuntu Linux. It is not the only way, but it seems to work. (Alternative instructions for installing the JDK on Linux are here.)

  1. Download the Java Development Kit

    As of this writing (28 Sep 2020) the latest version of the JDK is 15, which is available at

For example, I'm currently using jdk-15_linux-x64_bin.tar.gz, but you should pick the distribution that is most appropriate for your hardware and OS.

  1. Unpack the jdk tarchive with tar xvzf jdk-*.tar.gz (on the [cli] from inside the directory where you downloaded the jdk)

  2. Create the jvm directory with sudo mkdir -p /usr/lib/jvm.

  3. Move the jdk directory with `sudo mv jdk-15 /usr/lib/jvm/

  4. Make jdk-15 the default Java

    We will use the update-alternatives program for this step.

    (see also: notes on configuring JDK 1.7 on Ubuntu):

    This first block of 7 commands can be copy-and-pasted to the command line all at once:

     sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk-15/bin/java" 1;
     sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk-15/bin/javac" 1;
     sudo update-alternatives --install "/usr/bin/jcontrol" "jconsole" "/usr/lib/jvm/jdk-15/bin/jconsole" 1;
     sudo chmod a+x /usr/bin/java;
     sudo chmod a+x /usr/bin/javac;
     sudo chmod a+x /usr/bin/jconsole;
     sudo chown -R root:root /usr/lib/jvm/jdk-15;

    The following commands are interactive and should be invoked individually:

     sudo update-alternatives --config java
     sudo update-alternatives --config javac
     sudo update-alternatives --config jconsole

You can check which version of Java your system is currently using with the commandjava -version.

Add UACalc to Java Security Exceptions List

(As of March 2014, the Java security certificate for the UACalc has been renewed, so it shouldn't be necessary to follow all of the steps in this section. After installing Java as described above, and then following steps 1 and 2 below, the UACalc gui should run fine. However, I'll leave the information in this section as is, in case Ralph decides it's not worth renewing the security certificate in the future.)

In an ideal world, assuming you successfully installed Java as described in the previous step, you would now be able to go to and click a Launch button. However, the world is not idea, and launching UACalc for the first time now requires an extra step. We must first tell Java that we trust the site (This used to be a simple matter of checking a box, but Oracle has recently made the procedure for accepting security certificates even more annoying.)

  1. Get the uacalc.jnlp file
    Go to and download the uacalc.jnlp file that is most appropriate for your hardware. For example, if your machine has 8Gb of RAM, you probably want uacalcbig8.jnlp.

  1. Try to launch the UACalc gui (and probably fail)
    In a terminal window, go to the directory where you downloaded the file in the previous step and try to launch UACalc with the following command:

     javaws uacalcbig4.jnlp

    If UACalc starts up, you're good to go! More than likely, however, you will get an annoying dialog box like the following:

    Where is the checkbox on this dialog so that I can accept the risk and proceed at my own peril? It's gone. So we have no choice but to select the OK button to abort launch and follow the steps below.

  1. Launch the Java Control Panel
    At the command line, type jcontrol You should see a window that looks like this:

    If you get an error, try typing /usr/lib/jvm/jdk1.7.0/bin/jcontrol

  1. Add to the Exception Site List
    Click on the Security tab, and click the Edit Site List button. You should see a dialog box that looks like this:

    Click the Add button and type and click OK.

    You will get a warning. Click Continue.

    If your Java Control Panel now looks like the one below, click OK.

Launch UACalc

Now, when you invoke

    javaws ~/Desktop/uacalc/uacalcbig4.jnlp

at the command line, you should see a less futile and pointless window than the one we saw in Step 2.

Accept the risks and click OK and you should finally see the UACalc gui, which looks like this: