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Knowledgebase: ALMA Observing Tool (OT)
Why won't the OT work with Java 9?
Posted by Paul Fisher, Last modified by Gergö Popping on 18 February 2020 12:58 PM

Note that from Cycle 8 the appropriate version of Java is automatically included in the OT download package. OT Web Start is not supported anymore starting from Cycle 8.

There was a bug in Java 9 which prevents the Web Start version of the OT from opening when you try to run it. The only solution is to ensure that you have Java 8 on your system and use it to run the OT.

The download stops with an Application Error with the reason: factory already defined. In the details you will get the following exception:

java.lang.Error: factory already defined
at java.base/ Source)
at alma.obsprep.ot.gui.toplevel.ObservingToolWebstart.bug4648098(
at alma.obsprep.ot.gui.toplevel.ObservingToolWebstart.main(
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(Unknown Source)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(Unknown Source)
at java.base/java.lang.reflect.Method.invoke(Unknown Source)
at jdk.javaws@9.0.4/com.sun.javaws.Launcher.executeApplication(Unknown Source)
at jdk.javaws@9.0.4/com.sun.javaws.Launcher.executeMainClass(Unknown Source)
at jdk.javaws@9.0.4/com.sun.javaws.Launcher.doLaunchApp(Unknown Source)
at jdk.javaws@9.0.4/ Source)
at java.base/ Source)

You can check which version of Java you have by typing "java -version" at the command line, as described in the OT Troubleshooting instructions at

It is possible that this bug has now been fixed and we would appreciate any user feedback on this issue.

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