JTabbedPane

public class MyForm extends JFrame {
    JFrame window;
    JTabbedPane tab;
    public MyForm() {
        window = new JFrame("Товары");
        window.setSize(350,200);
        window.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        tab = new JTabbedPane();
        tab.addTab("Общие", new Pane_All());
        tab.addTab("Продукт", new Pane_Product());
        window.add(tab);
        window.setVisible(true);   
    }
 
public class Pane_Product extends JPanel {
    JLabel text;
    
    public Pane_Product(){
          JPanel mainPanel = new JPanel();
          mainPanel.setLayout(new BorderLayout());
          JPanel centerPanel = new JPanel();
          Border centerBorder = BorderFactory.createTitledBorder("CENTER panel");
          centerPanel.setBorder(centerBorder);
          mainPanel.add(centerPanel, BorderLayout.CENTER);
      
 
    }
}

JPanel mainPanel = new JPanel();

class Pane_Product extends JPanel {
    JLabel text;
 
    public Pane_Product() {
        setLayout(new BorderLayout());
        JPanel centerPanel = new JPanel();
        Border centerBorder = BorderFactory.createTitledBorder("CENTER panel");
        centerPanel.setBorder(centerBorder);
        add(centerPanel, BorderLayout.CENTER);
    }
}

JPanel mainPanel = new JPanel();