You specified the wrong class path. As your fully qualified class name is "test.twl.comps.NiceTree" which must be in this file and path:
where the element <classpath> is the root of the class path which needs to be specified. These are fundamental Java basics.
I corrected the path, but It's wrong so. But I got successful result, when I used .jar.
<?xml version="1.0" encoding="UTF8" standalone="yes"?>