class Line {
    private Vec3f point;
    /**
     * Normalized
     */
    private Vec3f direction;
    /**
     * For computing projections along line
     */
    private final Vec3f alongVec;

    /**
     * Default constructor initializes line to point (0, 0, 0) and
     * direction (1, 0, 0)
     */
    public Line() {
        point = new Vec3f(0, 0, 0);
        direction = new Vec3f(1, 0, 0);
        alongVec = new Vec3f();
        recalc();
    }

    /**
     * Line goes in direction <b>direction</b> through the point
     * <b>point</b>. <b>direction</b> does not need to be normalized but must
     * not be the zero vector.
     */
    public Line(Vec3f direction, Vec3f point) {
        direction = new Vec3f(direction);
        direction.normalize();
        point = new Vec3f(point);
        alongVec = new Vec3f();
        recalc();
    }

    /**
     * Direction is normalized internally, so <b>direction</b> is not
     * necessarily equal to <code>plane.setDirection(direction);
     * plane.getDirection();</code>
     */
    public Vec3f getDirection() {
        return direction;
    }

    /**
     * Setter does some work to maintain internal caches.
     * <b>direction</b> does not need to be normalized but must not be
     * the zero vector.
     */
    public void setDirection(Vec3f direction) {
        this.direction.set(direction);
        this.direction.normalize();
        recalc();
    }

    public Vec3f getPoint() {
        return point;
    }

    /**
     * Setter does some work to maintain internal caches.
     */
    public void setPoint(Vec3f point) {
        this.point.set(point);
        recalc();
    }

    /**
     * Project a point onto the line
     */
    public void projectPoint(Vec3f pt,
                             Vec3f projPt) {
        float dotp = direction.dot(pt);
        projPt.set(direction);
        projPt.scale(dotp);
        projPt.add(alongVec);
    }

    /**
     * Find closest point on this line to the given ray, specified by
     * start point and direction. If ray is parallel to this line,
     * returns false and closestPoint is not modified.
     */
    public boolean closestPointToRay(Vec3f rayStart,
                                     Vec3f rayDirection,
                                     Vec3f closestPoint) {
        // Line 1 is this one. Line 2 is the incoming one.
        Mat2f A = new Mat2f();
        A.set(0, 0, -direction.lengthSquared());
        A.set(1, 1, -rayDirection.lengthSquared());
        A.set(0, 1, direction.dot(rayDirection));
        A.set(1, 0, A.get(0, 1));
        if (Math.abs(A.determinant()) == 0.0f) {
            return false;
        }
        if (!A.invert()) {
            return false;
        }
        Vec2f b = new Vec2f();
        b.setX(point.dot(direction) - rayStart.dot(direction));
        b.setY(rayStart.dot(rayDirection) - point.dot(rayDirection));
        Vec2f x = new Vec2f();
        A.xformVec(b, x);
        if (x.y() < 0) {
            // Means that ray start is closest point to this line
            closestPoint.set(rayStart);
        } else {
            closestPoint.set(direction);
            closestPoint.scale(x.x());
            closestPoint.add(point);
        }
        return true;
    }

    //----------------------------------------------------------------------
    // Internals only below this point
    //

    private void recalc() {<FILL_FUNCTION_BODY>}
}

        float denom = direction.lengthSquared();
        if (denom == 0.0f) {
            throw new RuntimeException("Line.recalc: ERROR: direction was the zero vector " +
                "(not allowed)");
        }
        alongVec.set(point.minus(direction.times(point.dot(direction))));
    
<no_super_class>