发生这种情况是因为您将标签添加到 JPanel 中，该标签使用 FlowLayout 并将间隙作为默认设置.要解决此问题，您可以在接下来使用:

That happens because you add labels to JPanel which used FlowLayout with gaps as default. To fix that you can use next:

    JPanel line1 = new JPanel(new FlowLayout(FlowLayout.CENTER,0,0));
    JPanel line2 = new JPanel(new BorderLayout());