code: private void setClasses(DocEnv env, List<JCClassDecl> classes) {
          ListBuffer<ClassDocImpl> result = new ListBuffer<>();
          for (JCClassDecl def : classes) {
              //### Do we want modifier check here?
              if (env.shouldDocument(def.sym)) {
                  ClassDocImpl cd = env.getClassDoc(def.sym);
                  if (cd != null) {
                      cd.isIncluded = true;
                      result.append(cd);
                  } //else System.out.println(" (classdoc is null)");//DEBUG
              } //else System.out.println(" (env.shouldDocument() returned false)");//DEBUG
          }
          cmdLineClasses = result.toList();
      }
docs: Initialize classes information. Those classes are input from
  command line.
  
  @param env the compilation environment
  @param classes a list of ClassDeclaration