docs: public static Collection listPropertiesWithPrefix(Properties props, String prefix) {
          final HashSet set = new HashSet();
          for (Iterator i = props.keySet().iterator(); i.hasNext();) {
              String key = (String) i.next();
              if (key.startsWith(prefix)) {
                  set.add(props.getProperty(key));
              }
          }
          return set;
      }