Why does MATLAB crash at startup with the error "Cannot locate com/mathwo​rks/jmi/Op​aqueJavaIn​terface class"?

When I start MATLAB, I receive a "Fatal Error On Startup" window that says:

Cannot locate com/mathworks/jmi/OpaqueJavaInterface class

When I click the OK button, the window disappears and MATLAB does not start.

Answer 1

[MathWorks Support Team]

This error may occur if you have set a MATLAB_JAVA environment variable for a previous version of MATLAB. If this variable is set, you will need to unset it in order to run MATLAB. For more information on MATLAB_JAVA, see one of the following articles:

• How do I change the Java Virtual Machine (JVM) that MATLAB is using on Windows?
• How do I change the Java Virtual Machine (JVM) that MATLAB is using on macOS?
• How do I change the Java Virtual machine (JVM) that MATLAB is using on Linux?

This error can also be caused by a java.opts file on the MATLAB path. If you are using Windows and you have checked your path for java.opts files, but you are still receiving this error, make sure the "Start in" field in your shortcut is set to a directory that doesn't contain a java.opts file.

If MATLAB_JAVA is not set and java.opts is not present, then your MATLAB installation may be corrupt. Uninstall and reinstall MATLAB to repair your MATLAB installation. An installation of a different release of MATLAB may also work.

[Kouichi C. Nakamura]

I'm getting the same error

Cannot locate or initialize class com/mathworks/jmi/OpaqueJavaInterface.

on macOS 12.0.1. The link mentioned above:

• How do I change the Java Virtual Machine (JVM) that MATLAB is using on macOS?

is about how to change JVM. But it is not kind enough tell how to unset. Also, it says:

> This article applies only to MATLAB launched from a shell window or modified shortcut as both of these methods set-up the MATLAB_JAVA variable. Clicking on the regular MATLAB icon will not use the new Java.

My root problem is that I cannot lanch MATLAB by clicking. While investigating this issue, I found an article about launching MATLAB from Terminal, and I received the error above.

Can you elaborate a bit more what I should do next?

[Kouichi C. Nakamura]

Following the guide below, I tried Regenerate Preferences, and Start MATLAB from the Installation Folder with no avail. I deleted MATLAB and reinstalled it, and it launched eventually.

https://uk.mathworks.com/matlabcentral/answers/95806-why-will-matlab-not-start-up-properly-on-my-macos