Set a max zoom level on LatLngBounds builder

I have a similar case, where I want at least a map diagonal of 2 kilometers. Therefore I just add two additional points to the builder: the first 1 km north-west of the center of the original bounds and the second 1 km south-east of the center. If these are inside the bounds, they do not change anything. If they are outside of the original bounds, they increase the bounds to a meaningful size.

Here is a full code example:

public LatLngBounds createBoundsWithMinDiagonal(MarkerOptions firstMarker, MarkerOptions secondMarker) {
    LatLngBounds.Builder builder = new LatLngBounds.Builder();
    builder.include(firstMarker.getPosition());
    builder.include(secondMarker.getPosition());
    
    LatLngBounds tmpBounds = builder.build();
    /** Add 2 points 1000m northEast and southWest of the center.
     * They increase the bounds only, if they are not already larger
     * than this. 
     * 1000m on the diagonal translates into about 709m to each direction. */
    LatLng center = tmpBounds.getCenter();
    LatLng northEast = move(center, 709, 709);
    LatLng southWest = move(center, -709, -709);
    builder.include(southWest);
    builder.include(northEast);
    return builder.build();     
}

private static final double EARTHRADIUS = 6366198;
/**
 * Create a new LatLng which lies toNorth meters north and toEast meters
 * east of startLL
 */
private static LatLng move(LatLng startLL, double toNorth, double toEast) {
    double lonDiff = meterToLongitude(toEast, startLL.latitude);
    double latDiff = meterToLatitude(toNorth);
    return new LatLng(startLL.latitude + latDiff, startLL.longitude
            + lonDiff);
}

private static double meterToLongitude(double meterToEast, double latitude) {
    double latArc = Math.toRadians(latitude);
    double radius = Math.cos(latArc) * EARTHRADIUS;
    double rad = meterToEast / radius;
    return Math.toDegrees(rad);
}


private static double meterToLatitude(double meterToNorth) {
    double rad = meterToNorth / EARTHRADIUS;
    return Math.toDegrees(rad);
}

Edit, as this seems to be still well liked:

Please see https://stackoverflow.com/a/23092644/2808624 below: Nowadays one would use SphericalUtil for moving LatLng coordinates, instead of coding it on your own.

I implemented this solution according to the answer by user2808624, but using the SphericalUtil from the Android Maps Utility Library to do the calculations.

final double HEADING_NORTH_EAST = 45;
final double HEADING_SOUTH_WEST = 225;
LatLng center = tmpBounds.getCenter();
LatLng northEast = SphericalUtil.computeOffset(center, 709, HEADING_NORTH_EAST);
LatLng southWest = SphericalUtil.computeOffset(center, 709, HEADING_SOUTH_WEST);