public static void drawArrow(Graphics g, int x1, int y1, int x2, int y2, int lineWidth) {
   // Draw line using user defined drawline() which can specify line width
   drawLine(g, x1, y1, x2, y2, lineWidth);
   // Calculate x-y values for arrow head
   calcValues(x1, y1, x2, y2);
   g.fillPolygon(xValues, yValues, 3);
 }
 public static void drawLine(Graphics g, int x1, int y1, int x2, int y2, int lineWidth) {
   if (lineWidth == 1) g.drawLine(x1, y1, x2, y2);
   else {
     double angle;
     double halfWidth = ((double) lineWidth) / 2.0;
     double deltaX = (double) (x2 - x1);
     double deltaY = (double) (y2 - y1);
     if (x1 == x2) angle = Math.PI;
     else angle = Math.atan(deltaY / deltaX) + Math.PI / 2;
     int xOffset = (int) (halfWidth * Math.cos(angle));
     int yOffset = (int) (halfWidth * Math.sin(angle));
     int[] xCorners = {x1 - xOffset, x2 - xOffset + 1, x2 + xOffset + 1, x1 + xOffset};
     int[] yCorners = {y1 - yOffset, y2 - yOffset, y2 + yOffset + 1, y1 + yOffset + 1};
     g.fillPolygon(xCorners, yCorners, 4);
   }
 }