代码：

Example9_8.java

public class Example9_8

{

public static void main(String args[]){

WindowOperation win = new WindowOperation();

win.setBounds(100,100,390,360);

win.setTitle("简单计算器");

}

}

WindowOperation.java

import java.awt.*;

import javax.swing.*;

import java.io.*;

public class WindowOperation extends JFrame

{

JTextField inputNumberOne,inputNumberTwo;

JComboBox choiceFuhao;

JTextArea textShow;

JButton button;

OperatorListener operator;

ComputerListener computer;

public WindowOperation()

{

init();

setVisible(true);

setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);

}

void init(){

setLayout(new FlowLayout());

inputNumberOne = new JTextField(5);

inputNumberTwo = new JTextField(5);

choiceFuhao= new JComboBox();

button=new JButton("计算");

choiceFuhao.addItem("选择运算符号:");

String [] a={"+","-","*","/"};

for(int i=0;i

choiceFuhao.addItem(a[i]);

}

textShow=new JTextArea(9,30);

operator=new OperatorListener();

computer=new ComputerListener();

operator.setJComboBox(choiceFuhao);

operator.setWorkTogether(computer);

computer.setJTextFieldOne(inputNumberOne);

computer.setJTextFieldTwo(inputNumberTwo);

computer.setJTextArea(textShow);

choiceFuhao.addItemListener(operator);

button.addActionListener(computer);

add(inputNumberOne);

add(choiceFuhao);

add(inputNumberTwo);

add(button);

add(new JScrollPane(textShow));

}

}

OperatorListener.java

import java.awt.event.*;

import javax.swing.*;

public class OperatorListener implements ItemListener

{

JComboBox choice;

ComputerListener workTogether;

public void setJComboBox(JComboBox box){

choice =box;

}

public void setWorkTogether(ComputerListener computer){

workTogether=computer;

}

public void itemStateChanged(ItemEvent e){

String fuhao= choice.getSelectedItem().toString();

workTogether.setFuhao(fuhao);

}

}

ComputerListener.java

import java.awt.event.*;

import javax.swing.*;

public class ComputerListener implements ActionListener

{

JTextField inputNumberOne,inputNumberTwo;

JTextArea textShow;

String fuhao;

public void setJTextFieldOne(JTextField t){

inputNumberOne=t;

}

public void setJTextFieldTwo(JTextField t){

inputNumberTwo=t;

}

public void setJTextArea(JTextArea area){

textShow = area;

}

public void setFuhao(String s){

fuhao=s;

}

public void actionPerformed(ActionEvent e){

try{

double number1=Double.parseDouble(inputNumberOne.getText());

double number2=Double.parseDouble(inputNumberTwo.getText());

double result =0;

if(fuhao.equals("+")){

result=number1+number2;

}

else if(fuhao.equals("-")){

result=number1-number2;

}

else if(fuhao.equals("/")){

result=number1/number2;

}

else if(fuhao.equals("*")){

result=number1*number2;

}

textShow.append(number1+" "+fuhao+" "+number2+" = "+result+"\n");

}

catch(Exception exp){

textShow.append("\n请输入数字字符\n");

}

}

}

运行截图：