Error: java: Illegal char:

This is the IDEA problem - not your project.

The easiest way to solve it is to do the following: In the top panel of IDEA - > Archive - > Project Structure ( Ctrl + Alt + Shift + S ) - > Global Libraries - > " Delete " for the library " Juqery "

For some reason, when " api.jquery " is included as a Global Library - this will cause this error.