private String popString() {
    Object o = stack.pop();

    if (o instanceof StringBuilder) {
      StringBuilder sb = (StringBuilder) o;
      return sb.toString();

    } else {
      return (String) o;
    }
  }
Pops a <code>String</code> off of the stack.
geode-core/src/main/java/org/apache/geode/admin/internal/ManagedEntityConfigXmlParser.java