调整多个JPanel的大小

Question

我正在尝试让3个面板重新调整大小，我为它编写了代码。它应该工作。但事实并非如此。我正在制作3个JPanel组件，将它们添加到两个拆分窗格中，第一个拆分窗格包含中间面板和右侧面板。第二个分割窗格保持相同的中间面板和左侧面板，因此中间面板位于两个分割窗格中。

如果你能帮助我解决这个问题，我将非常感激。

public class FinalProjectTestCase1 {

public static void main(String[] args)
{
    Frame frame = new Frame();
    frame.pack();
    frame.setVisible(true);
    frame.setDefaultCloseOperation(frame.EXIT_ON_CLOSE);
}
}
class Frame extends JFrame 
{

JPanel LeftPanel;
JPanel MiddlePanel;
JPanel RightPanel;

Frame()
{
    this.setLayout(new BorderLayout());
    this.setPreferredSize(new Dimension(700,700));

    MiddlePanel= new JPanel();
    MiddlePanel.setLayout(new GridLayout());

    RightPanel= new JPanel();
    RightPanel.setLayout(new GridLayout());
    RightPanel.setPreferredSize(new Dimension(250,700));

    LeftPanel= new JPanel();
    LeftPanel.setLayout(new GridLayout());
    LeftPanel.setPreferredSize(new Dimension(250,700));

    JButton MiddlePanelb= new JButton("MiddlePanel");
    MiddlePanel.add(MiddlePanelb);

    JButton leftPanelb= new JButton("leftPanelb");
    LeftPanel.add(leftPanelb);

    JButton RightPanelb= new JButton("RightPanelb");
    RightPanel.add(RightPanelb);

    JSplitPane RightSplitPane= new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,(MiddlePanel),(RightPanel));
    JSplitPane LeftSplitPane= new JSplitPane(JSplitPane.HORIZONTAL_SPLIT,(LeftPanel),(MiddlePanel));

    this.add(MiddlePanel);
    this.add(RightSplitPane,BorderLayout.EAST);
    this.add(LeftSplitPane,BorderLayout.WEST);
}
}