Arrow.java

import java.awt.Graphics2D;
import java.awt.Stroke;
import java.awt.geom.GeneralPath;
import java.awt.geom.Point2D;

public enum Arrow {;

    public static void draw (final Graphics2D gfx, final Point2D start, final Point2D end, final Stroke lineStroke, final Stroke arrowStroke, final float arrowSize) {
  
      final double startx = start.getX();
      final double starty = start.getY();
  
      gfx.setStroke(arrowStroke);
      final double deltax = startx - end.getX();
      final double result;
      if (deltax == 0.0d) {
        result = Math.PI / 2;
      }
      else {
        result = Math.atan((starty - end.getY()) / deltax) + (startx < end.getX() ? Math.PI : 0);
      }
  
      final double angle = result;
  
      final double arrowAngle = Math.PI / 12.0d;
  
      final double x1 = arrowSize * Math.cos(angle - arrowAngle);
      final double y1 = arrowSize * Math.sin(angle - arrowAngle);
      final double x2 = arrowSize * Math.cos(angle + arrowAngle);
      final double y2 = arrowSize * Math.sin(angle + arrowAngle);
  
      final double cx = (arrowSize / 2.0f) * Math.cos(angle);
      final double cy = (arrowSize / 2.0f) * Math.sin(angle);
  
      final GeneralPath polygon = new GeneralPath();
      polygon.moveTo(end.getX(), end.getY());
      polygon.lineTo(end.getX() + x1, end.getY() + y1);
      polygon.lineTo(end.getX() + x2, end.getY() + y2);
      polygon.closePath();
      gfx.fill(polygon);
  
      gfx.setStroke(lineStroke);
      gfx.drawLine((int) startx, (int) starty, (int) (end.getX() + cx), (int) (end.getY() + cy));
    }
  
  }