MATLAB on Arch Linux: java.lang.NullPointerException and MATLAB does not start

If MATLAB stopped launching after a recent Arch Linux system update and you see a java.lang.NullPointerException with a stack trace starting at DTSingleClientFrame.mainFrameCreated, likely reason could be a corrupted preferences folder.

You can confirm the issue by checking whether MATLAB works without the desktop:

matlab -nodesktop -nosplash

If that launches fine, the desktop preferences are to blame. The fix is simply to delete MATLAB's local preferences folder:
rm -rf ~/.matlab/R20*/
matlab

MATLAB will recreate the folder fresh on next launch and the desktop should start normally again. No reinstall needed.