写了个计算器程序，编译没有问题，不过按键都是得到数字9，请高手指示

[Jesse_kang]

import java.awt.*;
import java.awt.event.*;
import java.text.DecimalFormat; //用于格式化十进制数字
import javax.swing.*;

public class Calculator {
private JFrame frame; //定义frame为JFrame类型 下同
private JPanel panel, panelKeys,panelKeys_up,panelKeys_down; //JPanel 是一般轻量级容器

private JTextField textCompute; //计算区域
//JTextField 是一个轻量级组件，它允许编辑单行文本

private JButton buttonBK, buttonC ; //定义退格键和清零键
private JButton button[]; //定义数字键
private JButton buttonDot,buttonAddandSub,buttonAdd,buttonSub,buttonMul,
buttonDiv,button1,button2,button3,buttonEqual; //运算符键

private double result; //运算结果
private final short Add=1; //+ 加
private final short Sub=2;//-减
private final short Mul=3; //× 乘
private final short Div=4; //除
private short operator =-1; //运算符

public Calculator()
{
frame =new JFrame("计算器");
panel =new JPanel();
frame.getContentPane().add(panel); //全局面板


ActionListener listener =new ComputeActionListener();

textCompute=new JTextField(15);//有关使用文本字段的信息和示例
textCompute.setText(""); //将此 TextComponent 文本设置为指定文本
textCompute.setEditable(false); //设置为不可编辑
textCompute.setBackground(Color.WHITE);

//功能键上半部
panelKeys_up=new JPanel();
panelKeys_up.setLayout(new FlowLayout(FlowLayout.RIGHT));
//FlowLayout流布局用于安排有向流中的组件，这非常类似于段落中的文本行
buttonBK=new JButton("BACK");
buttonBK.setForeground(Color.black);
buttonC=new JButton("C");
buttonC.setForeground(Color.black);
buttonBK.addActionListener(listener); //注册监听器
buttonC.addActionListener(listener);
panelKeys_up.add(buttonBK);
panelKeys_up.add(buttonC);

//功能键下半部
panelKeys_down=new JPanel();
panelKeys_down.setLayout(new GridLayout(4,5));
button=new JButton[10];
for(int i=0;i<10;i++) //定义数字键0-9
{
button[i]=new JButton(Integer.toString(i));//toString : 返回一个表示指定整数的 String 对象
button[i].setForeground(Color.black);
}
buttonDot=new JButton(".");
buttonDot.setForeground(Color.black);
buttonAddandSub=new JButton("+/-");
buttonAddandSub.setForeground(Color.black);
buttonAdd=new JButton("+");
buttonAdd.setForeground(Color.black);
buttonSub=new JButton("-");
buttonSub.setForeground(Color.black);
buttonDiv=new JButton("/");
buttonDiv.setForeground(Color.black);
buttonMul=new JButton("X");
buttonMul.setForeground(Color.black);
buttonEqual=new JButton("=");
buttonEqual.setForeground(Color.black);

button1=new JButton("");
button1.setForeground(Color.black);
button2=new JButton("");
button2.setForeground(Color.black);
button3=new JButton("");
button3.setForeground(Color.black);



panelKeys_down.add(button[1]);
panelKeys_down.add(button[2]);
panelKeys_down.add(button[3]);
panelKeys_down.add(buttonDiv);
panelKeys_down.add(buttonAddandSub);
panelKeys_down.add(button[4]);
panelKeys_down.add(button[5]);
panelKeys_down.add(button[6]);
panelKeys_down.add(buttonMul);
panelKeys_down.add(button2);
panelKeys_down.add(button[7]);
panelKeys_down.add(button[8]);
panelKeys_down.add(button[9]);
panelKeys_down.add(buttonSub);
panelKeys_down.add(button3);
panelKeys_down.add(button1);
panelKeys_down.add(button[0]);
panelKeys_down.add(buttonDot);
panelKeys_down.add(buttonAdd);
panelKeys_down.add(buttonEqual);

/*for(int i=0;i<10;i++) //定义数字键0-9
{
button[i].addActionListener(listener);//注册数字0-9
}*/
button[0].addActionListener(listener);
button[1].addActionListener(listener);
button[2].addActionListener(listener);
button[3].addActionListener(listener);
button[4].addActionListener(listener);
button[5].addActionListener(listener);
button[6].addActionListener(listener);
button[7].addActionListener(listener);
button[8].addActionListener(listener);
button[9].addActionListener(listener);

buttonDot.addActionListener(listener);
buttonAddandSub.addActionListener(listener);
buttonSub.addActionListener(listener);
buttonAdd.addActionListener(listener);
buttonDiv.addActionListener(listener);
buttonMul.addActionListener(listener);
buttonEqual.addActionListener(listener);

//加到功能面板
panelKeys=new JPanel();
panelKeys.setLayout(new BorderLayout());//这是一个布置容器的边界布局，它可以对容器组件进行安排
panelKeys.add(panelKeys_up,BorderLayout.NORTH);
panelKeys.add(panelKeys_down,BorderLayout.CENTER);

//加入到全局面板
frame.setLayout(new BorderLayout());
frame.add(textCompute,BorderLayout.NORTH);
frame.add(panelKeys,BorderLayout.SOUTH);

frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);//关闭是不执行任何操作
frame.setForeground(Color.blue);
frame.setSize(250,200);
frame.setResizable(false);
frame.setVisible(true);

//按键监听器

}

class ComputeActionListener implements ActionListener
{
/* ActionEvent指示发生了组件定义的动作的语义事件。当特定于组件的动作（比如被按下）发生时，
由组件（比如 Button）生成此高级别事件。事件被传递给每一个 ActionListener 对象，
这些对象是使用组件的 addActionListener 方法注册的，用以接收这类事件。 */
public void actionPerformed(ActionEvent event)
{
Object keyButton= event.getSource(); //最初发生 Event 的对象。
String text=textCompute.getText(); //getText 返回此 TextComponent 中包含的文本
DecimalFormat df=new DecimalFormat("0.########");//用于格式化十进制数字 //设置数据输出格式

//Back键
if(keyButton==buttonBK&&text.length()>0)
{
textCompute.setText(text.substring(0,text.length()-1));
}
//C键
if(keyButton==buttonC)
{
result=0;
textCompute.setText("");
}
//数字键
for(int i=0;i<=9;i++)
{
if(keyButton==button[i]);
{
textCompute.setText(text+i);
}
}

if ((keyButton == buttonAdd || keyButton == buttonSub || keyButton == buttonMul || keyButton == buttonDiv || keyButton == buttonEqual)) {
switch (operator) {
case Add:
result += Double.parseDouble(text);
break;
case Sub:
result -= Double.parseDouble(text);
break;
case Mul:
result *= Double.parseDouble(text);
break;
case Div:
if (Double.parseDouble(text) == 0) {
textCompute.setText("除数不能为零");
}
else
result /= Double.parseDouble(text);
break;
default:
result = Double.parseDouble(text);
}

textCompute.setText("");

if (keyButton == buttonAdd) {
operator = Add;
}
if (keyButton == buttonSub) {
operator = Sub;
}
if (keyButton == buttonMul) {
operator = Mul;
}
if (keyButton == buttonDiv) {
operator = Div;
}
if (keyButton == buttonEqual) {
operator = 0;
textCompute.setText(df.format(result));
}
}
if (keyButton == buttonDot && text.length() > 0 && text.indexOf(".") < 0) {
textCompute.setText(text + ".");
}

//+/-号键
if (keyButton == buttonAddandSub && text.length() > 0) {
double value = - Double.parseDouble(text);
textCompute.setText(df.format(value));
}

}
}
public static void main(String[] args)
{
new Calculator();
}
}

写了个计算器程序，编译没有问题，不过按键都是得到数字9，请高手指示
问题可能在红色代码部分。

[truediego]

判断哪个控件，用等号的啊？

[truediego]

// 数字键
			for (int i = 0; i <= 9; i++) {
				if (keyButton == button[i])
//这个分号是干啥的？？？？？
					;
				{
					textCompute.setText(text + i);
				}
			}

[Jesse_kang]

刚刚学java。原来就是一个分号的问题，看了很久，没有看出来

[Jesse_kang]

再问一个问题，把
if ((keyButton == buttonAdd || keyButton == buttonSub || keyButton == buttonMul || keyButton == buttonDiv || keyButton == buttonEqual))
{ switch (operator)
{ case Add: result += Double.parseDouble(text); break;
case Sub: result -= Double.parseDouble(text); break;
case Mul: result *= Double.parseDouble(text); break;
case Div:
if (Double.parseDouble(text) == 0)
{ textCompute.setText("除数不能为零"); }
else result /= Double.parseDouble(text); break;
default: result = Double.parseDouble(text); }
textCompute.setText("");
if (keyButton == buttonAdd)
{ operator = Add; }
if (keyButton == buttonSub) { operator = Sub; }
if (keyButton == buttonMul) { operator = Mul; }
if (keyButton == buttonDiv) { operator = Div; }
if (keyButton == buttonEqual)
{ operator = 0; textCompute.setText(df.format(result)); } }

换成

if(keyButton==buttonAdd)
{
result+=Double.parseDouble(text); //将String转为double
textCompute.setText("");
}
if(keyButton==buttonSub)
{
result-=Double.parseDouble(text); //将String转为double
textCompute.setText("");
}
if(keyButton==buttonMul)
{
result*=Double.parseDouble(text); //将String转为double
textCompute.setText("");
}
// if(keyButton==buttonDiv)
{
result/=Double.parseDouble(text); //将String转为double
textCompute.setText("");
}
if(keyButton==buttonEqual)
{
result=Double.parseDouble(text); //将String转为double
textCompute.setText("");
}

可不可以？？

[xtsqianli]

不明白 学习来了