Help would be so much appreciated new Irish Java programmer

Hi
I am a beginner java programmer and at the moment, I am learning about the Swing package. I was just wondering if anyone could help me with the code. When I compile it, I get the following 2 errors in cmd:
b1 is already defined in pizza()
and
setBorder in javax swing cannot be applied to pizza ButtonListener

Thank you so much if you can be of any help,
Joan

Code java:

import javax.swing.*;
import java.awt.event.*;
import javax.swing.border.*;
 
 
public class pizza extends JFrame 
 { 
 
 
	public static void main(String [] args)
	  {
 
 
			new pizza();
	   }
 
	private JButton buttonOK;
	private JRadioButton small, medium, large;
	private JCheckBox pepperoni, mushrooms, anchovies; 
 
 
	public pizza()
	{
	this.setSize(320,200);
	this.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
	this.setTitle("Order your pizza ");
 
	ButtonListener b1 = new ButtonListener();
 
	JPanel mainPanel = new JPanel();
 
	JPanel sizePanel = new JPanel(); 
 
	Border b1 = BorderFactory.createTitledBorder("Size");
	sizePanel.setBorder(b1);
 
	ButtonGroup sizeGroup = new ButtonGroup();
 
	small = new JRadioButton("Small");
	small.setSelected(true);
	sizePanel.add(small);
	sizeGroup.add(small);
 
	medium = new JRadioButton("medium");
 
	sizePanel.add(medium);
	sizeGroup.add(medium);
 
	large = new JRadioButton("large");
 
	sizePanel.add(large);
	sizeGroup.add(large);
 
	mainPanel.add(sizePanel);
 
	JPanel topPanel = new JPanel();
 
	Border b2 = BorderFactory.createTitledBorder("Toppings");
	topPanel.setBorder(b2);
 
	pepperoni = new JCheckBox("pepperoni");
	topPanel.add(pepperoni);
 
	mushrooms = new JCheckBox("Mushrooms");
	topPanel.add(mushrooms);
 
	anchovies = new JCheckBox("anchovies");
	topPanel.add(anchovies);
 
	mainPanel.add(topPanel);
 
 
	buttonOK = new JButton("OK");
	buttonOK.addActionListener(b1);
	mainPanel.add(buttonOK);
 
	this.add(mainPanel);
	this.setVisible(true);
 
 
	}
 
 
	private class ButtonListener implements ActionListener
	{
 
	public void actionPerformed(ActionEvent e)
	{
 
	if (e.getSource() == buttonOK)
	{
	String tops = "";
 
	if ( pepperoni.isSelected())
		tops += "pepperoni \n";
	if ( mushrooms.isSelected())
		tops += "mushrooms \n";
	if ( anchovies.isSelected())
		tops += "anchovies \n";
 
	String msg = " You ordered a " ;
	if ( small.isSelected())
		msg += "small pizza with " ;
	if ( medium.isSelected())
		msg += "medium pizza with " ;
	if ( large.isSelected())
		msg += "large pizza with " ;
 
 
	if (tops.equals(" "))
	msg += " no toppings";
	else
		msg += "the following toppings with : \n" + tops;
 
	JOptionPane.showMessageDialog(buttonOK, msg, "Your Order", JOptionPane.INFORMATION_MESSAGE);
 
	pepperoni.setSelected(false);
	mushrooms.setSelected(false);
	anchovies.setSelected(false);
	small.setSelected(true);
	}
 
	}
	}
}