public void label(String label) {
      if (!labelPattern.matcher(label).matches()) {
        throw new IllegalArgumentException(
            "Label '" + label + "' doesn't match acceptable label pattern.");
      }

      this.label = label;
    }
Specifies a single uppercase alphanumeric character from the set {A-Z, 0-9}.

@param label The label to add to markers.
src/main/java/com/google/maps/StaticMapsRequest.java