There's a copy of this class in jre/lib/rt.jar, which is the runtime. The class itself is part of the Xerces XML DOM manipulation library.
I'm not sure why you
IDE isn't picking it up, except that since a lot of apps use their own copy of Xerces, I wouldn't have expected to find it in the default JVM classpath.
The secret of how to be miserable is to constantly expect things are going to happen the way that they are "supposed" to happen.
You can have faith, which carries the understanding that you may be disappointed. Then there's being a willfully-blind idiot, which virtually guarantees it.