public double getAngle(Point prePoint, Point mPoint, Point nextPoint) {
    DefaultGeographicCRS crs = DefaultGeographicCRS.WGS84;
    GeodeticCalculator calc = new GeodeticCalculator(crs);
    calc.setStartingGeographicPoint(prePoint.getX(), prePoint.getY());
    calc.setDestinationGeographicPoint(mPoint.getX(), mPoint.getY());
    double azimuth1 = calc.getAzimuth();
    calc.setDestinationGeographicPoint(nextPoint.getX(), nextPoint.getY());

    double azimuth2 = calc.getAzimuth();
    double angle =azimuth2-azimuth1;
    return angle;
}