Why is there an error message when importing sun.swing in Java12?

Question

Java

I set import sun.swing.MenuItemLayoutHelper; the message package sun.swing is not visible
(package sun.swing is declared in module java.desktop, which does not export it to the unnamed module) appears. The java.desctop module has the sun.swing package. Help me understand what's going on.

Answer 1

The fact is that modules have appeared in Java since version 9. To connect modules, you need to describe them in your application using the module-info.java file, for example:
requires java.desktop;