code: public AbstractBuilder getClassBuilder(ClassDoc classDoc,
              ClassDoc prevClass, ClassDoc nextClass, ClassTree classTree)
              throws Exception {
          return ClassBuilder.getInstance(context, classDoc,
              writerFactory.getClassWriter(classDoc, prevClass, nextClass,
                  classTree));
      }
docs: Return the builder for the class.
  
  @param classDoc the class being documented.
  @param prevClass the previous class that was documented.
  @param nextClass the next class being documented.
  @param classTree the class tree.
  @return the writer for the class.  Return null if this
  writer is not supported by the doclet.