code: private void drawInterfere(Graphics g, int x1, int y1, int x2, int y2, int thickness, Color c) {
  
  		// The thick line is in fact a filled polygon
  		g.setColor(c);
  		int dX = x2 - x1;
  		int dY = y2 - y1;
  		// line length
  		double lineLength = Math.sqrt(dX * dX + dY * dY);
  
  		double scale = (double) (thickness) / (2 * lineLength);
  
  		// The x and y increments from an endpoint needed to create a
  		// rectangle...
  		double ddx = -scale * (double) dY;
  		double ddy = scale * (double) dX;
  		ddx += (ddx > 0) ? 0.5 : -0.5;
  		ddy += (ddy > 0) ? 0.5 : -0.5;
  		int dx = (int) ddx;
  		int dy = (int) ddy;
  
  		// Now we can compute the corner points...
  		int xPoints[] = new int[4];
  		int yPoints[] = new int[4];
  
  		xPoints[0] = x1 + dx;
  		yPoints[0] = y1 + dy;
  		xPoints[1] = x1 - dx;
  		yPoints[1] = y1 - dy;
  		xPoints[2] = x2 - dx;
  		yPoints[2] = y2 - dy;
  		xPoints[3] = x2 + dx;
  		yPoints[3] = y2 + dy;
  
  		g.fillPolygon(xPoints, yPoints, 4);
  	}
docs: 干扰线
  
  @param g {@link Graphics}
  @param x1x1
  @param y1 y1
  @param x2 x2
  @param y2 y2
  @param thickness 粗细
  @param c 颜色