How to remove the border of a component in Java Swing?

Question

Java

I am writing a plugin for Idea, and I ran into an unpleasant problem: a light gray frame is drawn around all components by default (see screenshot). How can it be removed?
I must say right away that this is most likely not a border, since the text editor has setBorder() set to black, but the white frame remains - you can see it on the screenshot.