code: protected void addModulesToIndexMap() {
          for (ModuleElement mdle : configuration.modules) {
              String mdleName = mdle.getQualifiedName().toString();
              char ch = (mdleName.length() == 0)
                      ? '*'
                      : Character.toUpperCase(mdleName.charAt(0));
              Character unicode = ch;
              SortedSet<Element> list = indexmap.computeIfAbsent(unicode,
                      c -> new TreeSet<>(comparator));
              list.add(mdle);
          }
      }
docs: Add all the modules to index map.