The following code when run on macOS 10.13 will select a bad font leading to unreadable text:

Font font = new Font(48.0f)

To reproduce this run the attached test program:

java MacFontBug

The program displays three strings, with three different fonts: the default System font, a newly-created 16 pt font, and a newly-created 48-point font. The first two display fine, but the third does not.

See the attached screen shot.

This is a regression introduced by the fix for JDK-8234916.