public NearbySearchRequest radius(int distance) {
    if (distance > 50000) {
      throw new IllegalArgumentException("The maximum allowed radius is 50,000 meters.");
    }
    return param("radius", String.valueOf(distance));
  }
Specifies the distance (in meters) within which to return place results. The maximum allowed
radius is 50,000 meters. Note that radius must not be included if {@code rankby=DISTANCE} is
specified.

@param distance The distance in meters around the {@link #location(LatLng)} to search.
@return Returns this {@code NearbyApiRequest} for call chaining.
src/main/java/com/google/maps/NearbySearchRequest.java