简易计算器

import java.awt.*;
import java.awt.event.ActionEvent;
import java.awt.event.ActionListener;
import java.awt.event.WindowAdapter;
import java.awt.event.WindowEvent;

public class Demo03 {
   Frame frame=new Frame("简易计算器");

   TextField textField1=new TextField(10);
   TextField textField2=new TextField(10);
   TextField textField3=new TextField(10);

   Choice choice=new Choice();

   Button button=new Button("=");

   public void init(){
       choice.add("+");
       choice.add("-");
       choice.add("*");
       choice.add("/");
       Panel panel=new Panel();
       panel.setLayout(new GridLayout(1,5));
       panel.add(textField1);
       panel.add(choice);
       panel.add(textField2);
       panel.add(button);
       panel.add(textField3);

       button.addActionListener(new ActionListener() {
           @Override
           public void actionPerformed(ActionEvent e) {
               String s1 = textField1.getText();
               String s2 = textField2.getText();
               int a=Integer.parseInt(s1);
               int b=Integer.parseInt(s2);
               int c=0;
               String s = choice.getSelectedItem();
               switch (s){
                   case "+":
                       c=a+b;
                       textField3.setText(String.valueOf(c));
                       break;
                   case "-":
                       c=a-b;
                       textField3.setText(String.valueOf(c));
                       break;
                   case "*":
                       c=a*b;
                       textField3.setText(String.valueOf(c));
                       break;
                   case "/":
                       if(b==0){
                           textField3.setText("错误");
                           break;
                       }else {
                           c = a / b;
                           textField3.setText(String.valueOf(c));
                           break;
                       }
               }
               textField1.setText("");
               textField2.setText("");
           }
       });
       frame.addWindowListener(new WindowAdapter() {
           @Override
           public void windowClosing(WindowEvent e) {
               System.exit(0);
           }
       });

       frame.add(panel);
       frame.pack();
       frame.setVisible(true);
   }

    public static void main(String[] args) {
        new Demo03().init();
    }

}

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