目標：1.點擊數字，在文本框中顯示;(完成)2.點擊START按鈕，觸發倒計時(再寫個倒計時的類),同時BUTTON上出現圖片;3.當時間為零時，圖片變樣；代碼：import javax.swing.*;import java.awt.*;import java.awt.event.ActionEvent;import java.awt.event.ActionListener;?public class MyFrame extends JFrame {?private JButton buttons[];public MyFrame(){super("Microwave");Container container=getContentPane();container.setLayout(new BorderLayout());JButton b=new JButton("START");JButton b1=new JButton("PUT YOUR FOOD!");JTextField field=new JTextField(20);container.add(b,BorderLayout.NORTH);Panel center=new Panel();Panel p=new Panel();center.setLayout(new BorderLayout());p.setLayout(new GridLayout(3,3));buttons = new JButton[9];buttons[0]=new JButton("7");buttons[1]=new JButton("8");buttons[2]=new JButton("9");buttons[3]=new JButton("4");buttons[4]=new JButton("5");buttons[5]=new JButton("6");buttons[6]=new JButton("1");buttons[7]=new JButton("2");buttons[8]=new JButton("3");for(int i=0;i<9;i++){p.add(buttons[i]); ?}for(int i=0;i<buttons.length;i++){buttons[i].addActionListener(new ActionListener() {@Overridepublic void actionPerformed(ActionEvent e) {field.setText(e.getActionCommand());}});}center.add(field, BorderLayout.NORTH);center.add(p, BorderLayout.CENTER);container.add(b1,BorderLayout.CENTER);container.add(center, BorderLayout.EAST);setVisible(true);setSize(450,300);}}}import javax.swing.*;import java.awt.*; ?public class Microwave { ???? ? public static void main(String[] args) { ?? ? ? ? MyFrame ceshi =new MyFrame();ceshi.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); ?? ? } ???} ?困難：主要實現第二個功能，如何通過點擊START按鈕來將文本框中的數字倒計時?。?？？望大神指教，十分感謝?。。?