Syntax error in SessionSettings.java/line 572 leading exception from java.util.regex

There is a syntax error in SessionSettings.java class, line 572.
original line: private final Pattern variablePattern = Pattern.compile("\\$

");
Should be: private final Pattern variablePattern = Pattern.compile("\\$

");

(with double slash before closing parenthesis).
This causes the failure in creating a SessionSettings instance.

I tried to recompile myself the corrected version, but I got the following exception:

java.lang.NoClassDefFoundError: quickfix.SessionSettings

Probably, you can suggest the possible solution.
Thank you!