public void setHint(final int numOfChildren) {
    final List<String> list = new ArrayList<>();
    for (int i = 0; i < numOfChildren; i++) {
      list.add(0, pop());
    }
    push(list);
  }
@return null if null is on the stack
geode-core/src/main/java/org/apache/geode/cache/query/internal/QCompiler.java