import java.awt.Container;import java.awt.FlowLayout;import java.awt.GridLayout;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;public class Exercise1 extends JFrame implements ActionListener{ private JPanel p1 = new JPanel(); //創(chuàng)建面板   private JPanel p2 = new JPanel(); //創(chuàng)建面板   private JTextField t1;  //文本框1用來(lái)顯示輸入信息   StringBuffer str;//輸入的字符串  JButton[] b=new JButton[10];  JButton b1,b2,b3,b4,b5,b6;//16個(gè)按鈕  double x,y;  int n; public Exercise1() {   super("假隊(duì)長(zhǎng)的大目標(biāo)");    setSize(350,300); //設(shè)置窗口大小   setLocationRelativeTo(null); //顯示到中間         Container c = getContentPane(); //創(chuàng)建內(nèi)容面板對(duì)象       t1 = new JTextField(25);     t1.setEditable(false); //只能顯示，不能編輯         p2.add(t1);  //添加文本框到面板     p2.setLayout(new GridLayout(3,2)); //把面扳布局為4行1列     str=new StringBuffer();     //實(shí)例化各個(gè)按鈕     for(int i=0;i<10;i++) //分別為數(shù)組中0~9號(hào)的按鈕設(shè)置標(biāo)簽，并注冊(cè)監(jiān)聽器     {      String s=""+i;      b[i]= new JButton(s);       b[i].addActionListener(this);      }         b1=new JButton("+");    b2=new JButton("-");    b3=new JButton("*");    b4=new JButton("/");      b5=new JButton("=");    b6=new JButton("delete");          //添加到面板    p1.add(b[7]);    p1.add(b[8]);    p1.add(b[9]);    p1.add(b1);    p1.add(b[4]);    p1.add(b[5]);    p1.add(b[6]);     p1.add(b2);    p1.add(b[1]);    p1.add(b[2]);    p1.add(b[3]);      p1.add(b3);    p1.add(b[0]);    p1.add(b5);    p1.add(b6);    p1.add(b4);       p1.setLayout(new GridLayout(4,5,10,10));         //注冊(cè)監(jiān)聽器          b1.addActionListener(this);    b2.addActionListener(this);    b3.addActionListener(this);    b4.addActionListener(this);    b5.addActionListener(this);    b6.addActionListener(this);      //將內(nèi)容添加到面板上然后添加到容器里    c.add(p2);     c.add(p1);     c.setLayout(new FlowLayout()); //設(shè)置為順序布局     //設(shè)置窗口關(guān)閉動(dòng)作     setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE); //設(shè)置窗口關(guān)閉動(dòng)作     setVisible(true); //設(shè)置為可見     setResizable(false); //禁止調(diào)整框架大小     }  public static void main(String[] args) { // TODO Auto-generated method stub @SuppressWarnings("unused") Exercise1 calculate=new Exercise1(); } @Override public void actionPerformed(ActionEvent e) { // TODO Auto-generated method stub   if(e.getSource()==b6){    t1.setText("0");//清零    t1.setHorizontalAlignment(JTextField.RIGHT);//右對(duì)齊    str.setLength(0); }             //Double.parseDouble  將字符串轉(zhuǎn)化為double類型       //t1.getText().trim()  獲取字符保存后并且清除      else if (e.getSource()==b1)//單擊加號(hào)按鈕獲得x的值并清空y的值    {     x=Double.parseDouble(t1.getText().trim());     str.setLength(0);     y=0d;     n=0;  }else if(e.getSource()==b2)//減法運(yùn)算  {  x=Double.parseDouble(t1.getText().trim());     str.setLength(0);     y=0d;    n=1; }else if(e.getSource()==b3)//乘法運(yùn)算 {  x=Double.parseDouble(t1.getText().trim());     str.setLength(0);     y=0d;    n=2; }else if(e.getSource()==b4)//除法運(yùn)算 {  x=Double.parseDouble(t1.getText().trim());     str.setLength(0);     y=0d;    n=3; }else if(e.getSource()==b5)//等號(hào) {  str.setLength(0);  switch(n){  case 0:t1.setText(""+(x+y));break;  case 1:t1.setText(""+(x-y));break;  case 2:t1.setText(""+(x*y));break;  case 3:t1.setText(""+(x/y));break;  }  }else{ if(e.getSource()==b[0]) {  if(t1.getText().trim().equals("0"))//如果顯示屏顯示的為零不做操作      {}      else  t1.setText(str.append(e.getActionCommand()).toString());  t1.setHorizontalAlignment(JTextField.RIGHT);   y=Double.parseDouble(t1.getText().trim());  } else     {     t1.setText(str.append(e.getActionCommand()).toString());     t1.setHorizontalAlignment(JTextField.RIGHT);     y=Double.parseDouble(t1.getText().trim());       } } } }