BasicStrokeで指定した辺の描画を行うBorderを作成する

class StrokeMatteBorder extends EmptyBorder {
  private final transient BasicStroke stroke;
  private final Paint paint;

  public StrokeMatteBorder(int top, int left, int bottom, int right,
                           BasicStroke stroke, Paint paint) {
    super(top, left, bottom, right);
    this.stroke = stroke;
    this.paint = paint;
  }

  @Override public void paintBorder(Component c, Graphics g,
                                    int x, int y, int width, int height) {
    float size = stroke.getLineWidth();
    if (size > 0f) {
      Insets insets = getBorderInsets(c);
      Graphics2D g2 = (Graphics2D) g.create();
      g2.setStroke(this.stroke);
      g2.setPaint(Objects.nonNull(this.paint)
                  ? this.paint : Objects.nonNull(c)
                  ? c.getForeground() : null);
      g2.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
                          RenderingHints.VALUE_ANTIALIAS_ON);
      g2.translate(x, y);

      int s = (int) (.5f + size);
      int sd2 = (int) (.5f + size / 2d);
      if (insets.top > 0) {
        g2.drawLine(0, sd2, width - s, sd2);
      }
      if (insets.left > 0) {
        g2.drawLine(sd2, sd2, sd2, height - s);
      }
      if (insets.bottom > 0) {
        g2.drawLine(0, height - s, width - s, height - s);
      }
      if (insets.right > 0) {
        g2.drawLine(width - sd2, 0, width - sd2, height - s);
      }
      g2.dispose();
    }
  }
}