窗口颜色

package bbb;
import java.awt.*;
import javax.swing.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
public class ccc {
    JFrame f;
    JPanel p;
    JButton b1,b2,b3;
    public ccc()
    {
        f=new JFrame();
        p=new JPanel();
        
        b1=new JButton("红色");
        b2=new JButton("绿色");
        b3=new JButton("蓝色");
        p.add(b1);p.add(b2);p.add(b3);
        f.add(p);
        f.add(p);
        f.add(p);
        b1.addActionListener(new ActionListener(){
            @Override
            public void actionPerformed(ActionEvent e){
                p.setBackground(Color.RED);
                        }});
        b2.addActionListener(new ActionListener(){
                         @Override
                         public void actionPerformed(ActionEvent e){
                            p.setBackground(Color.GREEN);
                        }});
        b3.addActionListener(new ActionListener(){
                         @Override
                         public void actionPerformed(ActionEvent e){
                             p.setBackground(Color.BLUE);
                        }});
         f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
                f.setSize(300, 200);
                 f.setVisible(true);
              }
              public static void main(String[] args) {
                 new ccc();
             }
}