新手求助，有关java面板的。请各位大神解答。

在一个框架里建立两个面板，各显示两幅图，不固定面板大小：
如果我固定面板大小，就只能显示一个面板

import java.awt.*;
import javax.swing.*;

public class SKK{
    public static void main (String[] args){
        JFrame frame= new JFrame("啦啦啦");
        frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
        int a= (int)(Math.random()*6+1);
        int b= (int)(Math.random()*6+1);
        int c= (int)(Math.random()*6+1);
        int d= (int)(Math.random()*6+1);
        
        JPanel panel1 =new JPanel();
        //panel1.setPreferredSize(new Dimension(50,100));
        panel1.setBackground(Color.green);
        ImageIcon Icon1=new ImageIcon("die0"+a+".png");
        JLabel label1=new JLabel(Icon1);
        panel1.add(label1);
        ImageIcon Icon2 =new ImageIcon("die0"+b+".png");
        JLabel label2=new JLabel(Icon2);
        panel1.add(label2);
        
        JPanel panel2 =new JPanel();
        //panel1.setPreferredSize(new Dimension(50,100));
        panel2.setBackground(Color.red);
        ImageIcon Icon3=new ImageIcon("die0"+c+".png");
        JLabel label3=new JLabel(Icon3);
        panel2.add(label3);
        ImageIcon Icon4=new ImageIcon("die0"+d+".png");
        JLabel label4=new JLabel(Icon4);
        panel2.add(label4);
        
        JPanel panel =new JPanel();
        panel.setBackground(Color.pink);
        panel.add(panel1);
        panel.add(panel2);
        
        frame.getContentPane().add(panel);
        frame.pack();
        frame.setVisible(true);
        
    }
}