数 - 递增错误

Question

我已经用Java创建了一个GUI程序，你可以在选择10秒，5分钟或1分钟后启动和停止计时器。这些数字会倒计时，但它们会在2中递增。所以它会变为10,8,6,4,2,0

其他一切工作正常，但我似乎无法弄清楚柜台有什么问题。这是我的代码。

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

public class countdownPanel extends JPanel
{

    private ImageIcon banner;
    private JComboBox selectCombo;
    private JButton stopButton, startButton;
    private JLabel picture, theCount;
    private Timer timer;

    public countdownPanel()
    {
        setLayout(new BorderLayout());
        setBackground(Color.black);

        //Banner Image
        banner = new ImageIcon ("banner.jpg");
        picture = new JLabel(banner);

        //Count Down selecter
        JComboBox selectCombo = new JComboBox();
        selectCombo.addItem("10 Seconds");
        selectCombo.addItem("1 Minute");
        selectCombo.addItem("5 Minutes");

        //countdown components
        theCount = new JLabel("   0");
        theCount.setFont(new Font("Helvetica", Font.BOLD, 200));

        timer = new Timer(1000, new TimerListener());

        //Stop Start Buttons
        startButton = new JButton("Start");
        stopButton = new JButton("Stop");

        ButtonListener listener = new ButtonListener();
        startButton.addActionListener(new ButtonListener());
        stopButton.addActionListener(new ButtonListener());
        selectCombo.addActionListener(new ComboListener());
        timer.addActionListener(new TimerListener());

        //GUI set up
        add(picture, BorderLayout.NORTH);
        add(startButton, BorderLayout.WEST);
        add(selectCombo, BorderLayout.CENTER);
        add(stopButton, BorderLayout.EAST);
        add(theCount, BorderLayout.SOUTH);

    }

//combo box listener
private class ComboListener implements ActionListener
{
    public void actionPerformed(ActionEvent event)
    {
        JComboBox levelCombo = (JComboBox) event.getSource();
        Object selected = levelCombo.getSelectedItem();

        if(selected.toString().equals("10 Seconds"))
            theCount.setText("10");

        if(selected.toString().equals("1 Minute"))
            theCount.setText("60");

        if(selected.toString().equals("5 Minutes"))
            theCount.setText("300");
    }
}

//Start and stop button listeners
private class ButtonListener implements ActionListener
{
    public void actionPerformed(ActionEvent event)
    {
        Object source = event.getSource();

        //starts timer
        if (event.getSource()== startButton)
            timer.start();

        //stops timer
        if (event.getSource()== stopButton)
            timer.stop();

    }
}

private class TimerListener implements ActionListener
{
    public void actionPerformed(ActionEvent event)
    {
        String A = theCount.getText();
        int count = Integer.parseInt(A);

        while(count < 0)
        {
            count--;
            theCount.setText(""+ count);
        }

        if(count == 0)
            theCount.setText(" GO!");
    }
    }
}