The following appears in the command window. What does it mean?java.​lang.NullP​ointerExce​ption

What does this mean: java.lang.NullPointerException in red many times.

[Walter Roberson]

There are a number of ways that can happen. We would need more information such as operating system and matlab version and what you were doing and whether there are additional messages.

Unfortunately a fair portion of the time the question needs to be sent to Support.

Answer 1

[Yair Altman]

This is an error that originates from Java code, typically concerning some GUI component that misbehavs or which does not handle some edge-case properly. You need to either adapt the way that you interact with that code (for example, ensure that you don't pass a Null pointer i.e. [] or {} as input argument), or ask the code's developers to handle this edge case.

Note that in a very large number of cases, you can safely ignore such command-window errors unless you see that there is really something wrong (for example, bad GUI rendering etc.). Yes they are indeed ugly and bothersome, but in many cases there are also harmless.

[Walter Roberson]

These errors can also occur due to internal MATLAB problems such as corrupted MATLAB installation. Also problems like this can show up if you are using your own JAVA.