code: int addType(final String value) {
      int hashCode = hash(Symbol.TYPE_TAG, value);
      Entry entry = get(hashCode);
      while (entry != null) {
        if (entry.tag == Symbol.TYPE_TAG && entry.hashCode == hashCode && entry.value.equals(value)) {
          return entry.index;
        }
        entry = entry.next;
      }
      return addType(new Entry(typeCount, Symbol.TYPE_TAG, value, hashCode));
    }
docs: Adds a type in the type table of this symbol table. Does nothing if the type table already
  contains a similar type.
  
  @param value an internal class name.
  @return the index of a new or already existing type Symbol with the given value.