code: public final void addBin(@NotNull final BinClasspathEntry entry) {
          Contract.requireArgNotNull("entry", entry);
          if (binList == null) {
              binList = new ArrayList<>();
          }
          binList.add(entry);
      }
docs: Adds a classes directory to the list. If the list does not exist it's created.
  
  @param entry
  Binaries directory to add.