监视器

//y.java
public class y {

	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.*;

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

//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");
      }
   }
}