code: public void addCatchClause(CatchClause clause) {
          assertNotNull(clause);
          if (catchClauses == null) {
              catchClauses = new ArrayList<CatchClause>();
          }
          catchClauses.add(clause);
          clause.setParent(this);
      }
docs: Add a catch-clause to the end of the list, and sets its parent to
  this node.
  @throws IllegalArgumentException} if {@code clause} is {@code null}