JMenuBar按钮无响应

Question

尝试使用JMenuBar和JMenu制作转换计算器，但是我似乎无法让动作侦听器工作，因为当用户从菜单中选择一个选项时，我的GUI不会执行任何操作。我感觉它与Object源或我的if语句有问题，但我真的不确定，因为这是我第一次使用JMenus。有人能告诉我我做错了什么吗？非常感谢！

 import javax.swing.*;
 import java.awt.*;
 import java.awt.event.ActionListener;
 import javax.swing.JFrame;
 import java.awt.event.*;

 public class ConversionMenu extends JFrame implements ActionListener
 {
   Object[] choice;
   double input;
   double peso1, yen1, euro1;
   String output;
   JLabel num = new JLabel("How much would you like to convert:   ");
   JTextField n1 = new JTextField(10);
   JLabel money = new JLabel();
   JFrame frame = new JFrame();
   JLabel result = new JLabel("");
   JButton clear = new JButton("Clear");
   JMenuBar menubar = new JMenuBar();
   JMenu menu = new JMenu("Convert");
   JMenu peso = new JMenu("To Mexican Peso");
   JMenu yen = new JMenu("To Japanese Yen");
   JMenu euro = new JMenu("To European Euro");
   JMenu close = new JMenu("Close");

  public ConversionMenu()
    {
       FlowLayout flow = new FlowLayout();
       JPanel pane = new JPanel();
       pane.setLayout(flow);
       pane.add(num);
       pane.add(n1);
       pane.add(clear);
       pane.add(result);
       frame.setJMenuBar(menubar);
       menubar.add(menu);
       menu.add(peso);
       peso.addActionListener(this);
       menu.add(yen);
       yen.addActionListener(this);
       menu.add(euro);
       euro.addActionListener(this);
       JMenu exit = new JMenu("Exit");
       menubar.add(exit);
       exit.add(close);
       close.addActionListener(this);
       setJMenuBar(menubar);
       setContentPane(pane);
   }
   public void actionPerformed(ActionEvent a)
     {      
      Object source = a.getSource();
      choice = menu.getSelectedObjects();
      input = Double.parseDouble(n1.getText());

       if(source == peso);
           {
           peso1 = input*19.08;
           output = String.format("$" + n1 + "American dollars is 
           equal to " + peso1 + "Mexican pesos.");
           result.setText(output);
            }
       if (source == yen)
           {
           yen1 = input*113.78;
           output = String.format("$" + n1 + "American dollars is equal 
           to " + yen1 + "Japanese yen.");
           result.setText(output);
           }
          else if (source == euro)
           {
            euro1 = input*0.86;
            output = String.format("$" + n1 + "American dollars is 
            equal to " + euro1 + "European euro.");
            result.setText(output);
            }
          else if (source == close)
           {
              System.exit(0);
           }
         if(source == clear)
          {
            n1.setText("");
            result.setText("");
           }

      }
public static void main(String[] args)
  {
    ConversionMenu con = new ConversionMenu();
    con.setTitle("Money Conversion Calculator");
    con.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    con.setSize(500, 500);
    con.setVisible(true);
  }
}