Java installation

Ancestris needs Java and is compatible with Java versions 8 to 21.

If Ancestris does not start, or shows the Ancestris splash screen and stops, it is most generally related to an issue with the Java installation. Either Java is not installed or Ancestris does not find it or finds an incompatible version or finds a corrupted version.

The following sections offer a step-by-step check to ensure Ancestris is using a valid Java version.

General principle

Install Java

A simple way to get an official Java version is to get it from

If Java is not installed or if you want the latest or a specific version of Java, just download it from the site above.

Identify if Java is already installed

If you don't know if Java is installed or which version is installed, open a command line terminal and type the command line:

java -version
java version "1.8.0_251"
Java(TM) SE Runtime Environment (build 1.8.0_251-b08)
Java HotSpot(TM) 64-Bit Server VM (build 25.251-b08, mixed mode)

According to the display above, we can see that the installed Java version set by default is version 1.8, aka version 8.

If you have a Java version installed as per the example above, and are happy to use this version, you may disregard the rest of this page. 


If Java is installed and Ancestris does not start, either Ancestris does not find Java or finds an incompatible version or finds a corrupted version.

Whether only one version of Java or several versions are installed on your system, you will then need to check and potentially update the configuration file to tell Ancestris where to look for Java.

Rather than changing the Ancestris configuration file, and if several version of Java are available on your system, an alternative would be to change the default Java version.

Update the Ancestris configuration file 

You only need to worry about what is detailed below if Java is installed and Ancestris does not start.

You need to update the Ancestris configuration file to tell where Ancestris should look for Java, if Ancestris does not seem to find it.

The principle is the following:

Ancestris uses two configuration files, both named ancestris.conf
1/ The first one is the Application Configuration file, which is part of the Application directory and it is created during the installation of Ancestris. 
2/ The other one is the User Configuration file, which is part of your User directory, and created when you change some Preferences when using Ancestris.

The User Configuration file takes precedence over the Application Configuration file 

So the configuration file to check and update is the User Configuration file if it exists, the Application Configuration file otherwise.
- If you are installing Ancestris, you will probably need to update the Application Configuration file.
- If you have already used Ancestris and want to change the java version, you will probably need to update the User Configuration file. 

Chech here to know where the configuration file is depending on your system.

The path to Java in the configuration file

So open the configuration file with a regular text editor.

1. Check the line defining default_options

This line should look like this:

default_options="--branding ancestris -J-Xms96m -J-Xmx1g --laf javax.swing.plaf.nimbus.NimbusLookAndFeel"

If one of the options in this line includes --jdkhome="/path/to/java, make sure the path specified in this option is the path to the Java version you want to use. 

If this line does not include a java path, locate jdkhome elsewhere.

2. Check the line defining jdkhome

If the line looks like jdkhome="/path/to/java", then make sure the path specified in this option is the path to the Java version you want to use. 

If the line starts with "#", a comment markup, Ancestris will disregard as if it did not exist.

If Ancestris does not start, it could be that the jdkhome folder name is incorrectly spelt or points to an incorrect Java version.

Whatever your operating system is, if the default active Java version is different from the one to be used with Ancestris, you have to modify the jdkhome line like this:


Case of macOS

For macOS, if for example Java 21 and Java 17 are installed on your Mac and you want to force the use of Java 17 for Ancestris, the complete manipulation to force the version of Java would be the following:

Case of Windows and Linux

For Windows or Linux for example, if the java executable is /usr/java/jdk1.8.0_291-amd64/bin/java, then you must indicate


Note: you have to exclude /bin/java in the path description.

Change the default Java versions in case multiple versions are installed

If several versions are available on your systems and you need to swap Java versions so that Ancestris uses the default one, the swap procedure depends on your operative system.

Swap default version for macOS

To swap between different Java versions, open a Terminal window and follow the steps below.

In the following example, the instructions let you set Version 8 (aka 1.8) by default, without removing Java Version 10:

1/6 - Check which version of Java is set by default

java -version
echo $jdkhome

You can see the java version you are running.

2/6 - Get a list of all installed versions on your system and check Version 8 or 11 is among them

/usr/libexec/java_home -V

If the version you want is not in the list, then install it as explained in this section.

If it is in the list, but not the one you had above, force the path to the java version with the following step.

3/6 - Type in the following 2 lines in the Terminal

echo 'export JAVA_HOME=`/usr/libexec/java_home -v 1.8`' >>~/.bash_profile
echo 'export jdkhome==`/usr/libexec/java_home -v 1.8`' >>~/.bash_profile

These two lines will add the command to set your default Java version in your personal profile. Here, we force version 1.8 (or 8). Replace with your java version.

The first line defines the default Java version for all programs (JAVA_HOME, in uppercase).

The second line defines the default Java version to use for Ancestris (jdkhome, lowercase).

4/6 - Close the Terminal


5/6 - Reopen a Terminal and check that the running Java is now the one you want (version 8 in our example)

java -version
echo $jdkhome

You can now start Ancestris.

6/6 - Start Ancestris

When Ancestris starts, a Terminal window opens at the same time.

You can see in the title bar that version 8 of Java is being used by Ancestris.

Swap default version for Windows

You have to create a BAT file per Java version you wish to keep.

Use your favourite text editor to create those files, using the code below, and place them in a folder available from your PATH.


@echo off
echo Setting JAVA_HOME
set JAVA_HOME=C:\Program Files\Java\jdk1.8.0_12
echo setting PATH
set PATH=C:\Program Files\Java\jdk1.8.0_12\bin;%PATH%
echo Display java version
java -version


@echo off
echo Setting JAVA_HOME
set JAVA_HOME=C:\Program Files\Java\jdk1.11.0_11
echo setting PATH
set PATH=C:\Program Files\Java\jdk1.11.0_11\bin;%PATH%
echo Display java version
java -version

While creating these files, make sure you specify the correct name for the Java files for the lines JAVA_HOME, depending on your Java installation

When you decide to change the Java version, just run the corresponding BAT file: JAVA8 for version 1.8, or JAVA11 for version 11. The Java version at use will be shown on the terminal.

To check if the change is really in effect, type java -version on a console or check this page.

Swap default version for Linux

Type the following on a console :

sudo update-alternatives --config java


Select from the list the version needed.

To get help using this tool :

sudo update-alternatives -l

Revision #110
Created 24 May 2020 16:53:31 by frederic
Updated 9 June 2024 11:59:35 by frederic