Calculates the distance of a location point to the line constructed by other 2 location points and checks whether or not the location point is close enough to the line to be on it

DistanceOfPointToLine.java

/* If the distance between location point and line is less than this, point is considered to be on the line */
public static final double POINT_DISTANCE_TO_LINE_THRESHOLD = 0.01;

/* Calculates the distance of a location point to the line constructed by other 2 location points */
public double distanceOfPointToTheLine(Location location, Location point1, Location point2) {
    double x0 = location.getLatitude();
    double y0 = location.getLongitude();

    double x1 = point1.getLatitude();
    double y1 = point1.getLongitude();

    double x2 = point2.getLatitude();
    double y2 = point2.getLongitude();

    double a = y2 - y1;
    double b = x1 - x2;
    double c = (x2 * y1) - (x1 * y2);

    return Math.abs((a * x0) + (b * y0) + c) / Math.sqrt((a * a) + (b * b));
}

/* Checks whether or not the location point is close enough to the line constructed by other 2 location points to be on it */
public boolean isPointCloseToOrOnTheLine(Location location, Location point1, Location point2) {
    return distanceOfPointToTheLine(location, point1, point2) <= POINT_DISTANCE_TO_LINE_THRESHOLD;
}

Assume Location type to have latitude and longitude as double values accessible via getLatitude() and getLongitude() methods respectively.