code: protected JavaSource getJavaSourceForClass(String clazzname) {
      String resource = clazzname.replaceAll("\\.", "/") + ".java";
      FileObject fileObject = classPath.findResource(resource);
      if (fileObject == null) {
        return null;
      }
      Project project = FileOwnerQuery.getOwner(fileObject);
      if (project == null) {
        return null;
      }
      SourceGroup[] sourceGroups = ProjectUtils.getSources(project).getSourceGroups("java");
      for (SourceGroup sourceGroup : sourceGroups) {
        return JavaSource.create(ClasspathInfo.create(sourceGroup.getRootFolder()));
      }
      return null;
    }
docs: Resolves the clazzname to a fileobject of the java-file
  
  @param clazzname
  @return null or the fileobject