Class Line2D

src/main/java/org/htmlunit/util/geometry/Line2D.java:22–141

Simple 2D shape line. @author Ronald Brill

 * @author Ronald Brill
 */
public class Line2D implements Shape2D {

    private final double startX_;
    private final double startY_;
    private final double endX_;
    private final double endY_;
    private final boolean isVertical_;

    private final double slope_;
    private final double yIntercept_;

    /**
     * Ctor.
     * @param start the start point
     * @param end the end point
     */
    public Line2D(final Point2D start, final Point2D end) {
        this(start.getX(), start.getY(), end.getX(), end.getY());
    }

    /**
     * Ctor.
     * @param x1 the x value of the start point
     * @param y1 the y value of the start point
     * @param x2 the x value of the end point
     * @param y2 the y value of the end point
     */
    public Line2D(final double x1, final double y1, final double x2, final double y2) {
        startX_ = x1;
        startY_ = y1;
        endX_ = x2;
        endY_ = y2;

        isVertical_ = Math.abs(startX_ - endX_) < EPSILON;
        if (isVertical_) {
            slope_ = Double.NaN;
            yIntercept_ = Double.NaN;
        }
        else {
            // y = slope * x + b
            slope_ = (endY_ - startY_) / (endX_ - startX_);
            yIntercept_ = startY_ - slope_ * startX_;
        }
    }

    /**
     * @param line the line to intersect this with
     * @return the intersection point of the two lines or null if they are parallel
     */
    public Point2D intersect(final Line2D line) {
        if (isVertical_ && line.isVertical_) {
            return null;
        }

        if (isVertical_ && !line.isVertical_) {
            final double intersectY = line.slope_ * startX_ + line.yIntercept_;
            return new Point2D(startX_, intersectY);
        }