java计算器

import java.awt.*;
import java.awt.event.*;
import java.applet.Applet;
import javax.swing.*;
public class apl extends Applet implements ActionListener 
{
 double a=0,b=0;
 char c=' ';
 JTextField field1=new JTextField(18);
 JTextField field2=new JTextField(18);
 JButton button1=new JButton("+");
 JButton button2=new JButton("-");
 JButton button3=new JButton("*");
 JButton button4=new JButton("/");
 JButton button5=new JButton("平方");
 JButton button6=new JButton("开平方");
 JButton button7=new JButton("=");
 JButton button8=new JButton("重置");
 public void init() 
 {  // 初始化
  this.setSize(250, 200);
  add(field2);    add(field1);    
  add(button1);   add(button2);   
  add(button3);   add(button4);   
  add(button5);   add(button6);   
  add(button7);   add(button8);
  button1.addActionListener(this);
  button2.addActionListener(this);
  button3.addActionListener(this);
  button4.addActionListener(this);
  button5.addActionListener(this);
  button6.addActionListener(this);
  button7.addActionListener(this);
  button8.addActionListener(this);
  }
  
//加
  public void dobutton1()//加
  {  // 处理按钮事件
   if(a==0&&c==' ')
   {
    a=Double.parseDouble(field1.getText());
   }
   else
   {
    b=Double.parseDouble(field1.getText());
    if(c=='+')
    {
     a+=b;
    }
    if(c=='-')
    {
     a-=b;
    }
    if(c=='*')
    {
     a*=b;
    }
    if(c=='/')
    {
     a/=b;
    }
    if(c=='^')
    {
     a*=a;
    }
    if(c=='&')
    {
     a=Math.sqrt(a);
    }
   }
   c='+';
   field2.setText(field2.getText()+Double.toString(b==0?a:b)+c);
   field1.setText("  ");
  }
  public void dobutton2()//减
  {  // 处理按钮事件
   if(a==0&&c==' ')
   {
    a=Double.parseDouble(field1.getText());
   }
   else
   {
   b=Double.parseDouble(field1.getText());
   if(c=='+')
   {
    a+=b;
  }
   if(c=='-')
    {
     a-=b;
    }
    if(c=='*')
    {
     a*=b;
    }
    if(c=='/')
    {
     a/=b;
    }
    if(c=='^')
    {
     a*=a;
    }
    if(c=='&')
    {
     a=Math.sqrt(a);
    }
   }
   c='-';
   field2.setText(field2.getText()+Double.toString(b==0?a:b)+c);
   field1.setText("  ");
  }
  public void dobutton3()//乘
  {  // 处理按钮事件
   if(a==0&&c==' ')
   {
    a=Double.parseDouble(field1.getText());
   }
   else
   {
   b=Double.parseDouble(field1.getText());
   if(c=='+')
   {
    a+=b;
   }
   if(c=='-')
    {
     a-=b;
    }
    if(c=='*')
    {
     a*=b;
    }
    if(c=='/')
    {
     a/=b;
    }
    if(c=='^')
    {
     a*=a;
    }
    if(c=='&')
    {
     a=Math.sqrt(a);
    }
   }
   c='*';
   field2.setText(field2.getText()+Double.toString(b==0?a:b)+')'+c);
   field1.setText("  ");
  }
  public void dobutton4()//除
  {  // 处理按钮事件
   if(a==0&&c==' ')
   {
    a=Double.parseDouble(field1.getText());
   }
   else
   {
   b=Double.parseDouble(field1.getText());
   if(c=='+')
   {
    a+=b;
  }
   if(c=='-')
    {
     a-=b;
    }
    if(c=='*')
    {
     a*=b;
    }
    if(c=='/')
    {
     a/=b;
    }
    if(c=='^')
    {
     a*=a;
    }
    if(c=='&')
    {
     a=Math.sqrt(a);
    }
   }
   c='/';
   field2.setText(field2.getText()+Double.toString(b==0?a:b)+')'+c);
   field1.setText("  ");
  }
  public void dobutton5()//平方
  {  // 处理按钮事件
   if(a==0&&c==' ')
   {
    a=Double.parseDouble(field1.getText());
   }
   else
   {
   b=Double.parseDouble(field1.getText());
   if(c=='+')
   {
    a+=b;
  }
   if(c=='-')
    {
     a-=b;
    }
    if(c=='*')
    {
     a*=b;
    }
    if(c=='/')
    {
     a/=b;
    }
    if(c=='^')
    {
     a*=a;
    }
    if(c=='&')
    {
     a=Math.sqrt(a);
    }
   }
   c='^';
   field2.setText(field2.getText()+Double.toString(b==0?a:b)+c);
   field1.setText("  ");
  }
  public void dobutton6()//开方
  {  // 处理按钮事件
   if(a==0&&c==' ')
   {
    a=Double.parseDouble(field1.getText());
   }
   else
   {
   b=Double.parseDouble(field1.getText());
   if(c=='+')
   {
    a+=b;
  }
   if(c=='-')
    {
     a-=b;
    }
    if(c=='*')
    {
     a*=b;
    }
    if(c=='/')
    {
     a/=b;
    }
    if(c=='^')
    {
     a*=a;
    }
    if(c=='&')
    {
     a=Math.sqrt(a);
    }
   }
   c='&';
   field2.setText(field2.getText()+Double.toString(b==0?a:b)+c);
   field1.setText("  ");
  }
  public void dobutton7()//=
  {
   if(a==0&&c==' ')
   {
    a=Double.parseDouble(field1.getText());
   }
   else
   {
     if(c=='+')
     {
      b=Double.parseDouble(field1.getText());
      a+=b;
      }
     if(c=='-')
     {
      b=Double.parseDouble(field1.getText());
      a-=b;
      }
     if(c=='*')
     {
      b=Double.parseDouble(field1.getText());
      a*=b;
      }
     if(c=='/')
     {
      b=Double.parseDouble(field1.getText());
      a/=b;
      }
     }
    if(c=='^')
    {
     a=a*a;
    }
    if(c=='&')
    {
     a=Math.sqrt(a);
    }
   
   field1.setText(a+"");
   field2.setText(field2.getText()+Double.toString(b==0?a:b)+'=');
   b=0;
   c=' ';
  }
  public void dobutton8()//重置
  {  // 处理按钮事件
   field1.setText(" ");
   field2.setText(" ");
   c=' ';
   a=0;
   b=0;
  }
//事件源处理
public void actionPerformed(ActionEvent e)
{
 Object obj;
 obj=e.getSource();
 if(obj==button1)
 {
  dobutton1();
 }else if(obj==button2)
 {
  dobutton2();
 }else if(obj==button3)
 {
  dobutton3();
 }else if(obj==button4)
 {
  dobutton4();
 }else if(obj==button5)
 {
   dobutton5();
 }else if(obj==button6)
 {
  dobutton6();
 }else if(obj==button7)
 {
   dobutton7();
 }else if(obj==button8)
 {
   dobutton8();
 }
}
}