java倒计时弹出框

直接使用java语言写出一个运行时的弹出框倒计时：
package test.dagong.testDecreaseDate;

import java.awt.Container;
import java.awt.FlowLayout;
import java.awt.Toolkit;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;

import javax.swing.JButton;
import javax.swing.JFrame;
import javax.swing.JPanel;
import javax.swing.JTextField;
import javax.swing.Timer;

@SuppressWarnings(“unused”)
public class TestDecreaseDate extends JFrame implements ActionListener {

private static final long serialVersionUID = 4603262282860990473L;

private static final int DEFAULT_WIDTH = 200;
private static final int DEFAULT_HEIGHT = 100;
private static final int width = Toolkit.getDefaultToolkit()
        .getScreenSize().width;
private static final int height = Toolkit.getDefaultToolkit()
        .getScreenSize().height;
private Container container;
private JButton btn;
private JTextField jtfTime;
private Timer tmr;

public TestDecreaseDate() {
    initComponents();
    Timer tmr = new Timer(1000, this);
    this.tmr = tmr;
    setVisible(true);
}
private void initComponents() {
    this.setTitle("SY秒表");
    this.setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);
    this.setResizable(false);
    setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
    this.setLocation((width - DEFAULT_WIDTH) / 2,
            (height - DEFAULT_HEIGHT) / 2);
    jtfTime = new JTextField("10000");
    btn = new JButton("开始倒计时");
    container = getContentPane();
    JPanel panel = new JPanel();
    panel.add(btn);
    panel.add(jtfTime);
    this.add(panel);
    btn.addActionListener(this);
}
public void actionPerformed(ActionEvent ae) {
    if (ae.getSource() == btn) {
        jtfTime.setText("10");
        tmr.start();
    } else {
        int t;
        t = Integer.parseInt(jtfTime.getText());
        t--;
        jtfTime.setText("" + t);

        if (t <= 0) {
            tmr.stop();
        }
    }
}
public static void main(String[] args) {
    TestDecreaseDate timeController = new TestDecreaseDate();
}

}