张龄心是谁的女儿:java中如何进行减法运算

我写了一个程序，用三个文本框和四个按扭，在文本框中输入要计算的数字，四个按扭分别是加减乘除，结果在第三个文本框中显示，可是在编译的时候提示问题是operator-cannot be applied to java.lang.String,double text3.setText(""+number1-number2);
源程序是
import java.applet.*;
import java.awt.*;
import java.awt.event.*;
public class Work10_3 extends Applet implements ActionListener
{
TextField text1,text2,text3;
Button button1,button2,button3,button4;
public void init()
{ text1=new TextField(10);add(text1);
text2=new TextField(10);add(text2);
text3=new TextField(30);add(text3);
button1=new Button("加");
button2=new Button("减");
button3=new Button("乘");
button4=new Button("除");
add(text1);add(text2);add(text3);
add(button1);add(button2);add(button3);add(button4);
button1.addActionListener(this);
button2.addActionListener(this);
button3.addActionListener(this);
button4.addActionListener(this);
}
public void paint(Graphics g)
{
g.drawString("将前两个文本框中的数字进行相应操作",10,100);
g.drawString("结果显示于最后的文本框",10,100);
}
public void actionPerformed(ActionEvent e)
{double number1=0,number2=0;
if(e.getSource()==button1)
{
try{ number1=Double.valueOf(text1.getText()).doubleValue();
number2=Double.valueOf(text1.getText()).doubleValue();
text3.setText(""+number1+number2);
}
catch(NumberFormatException event)
{ text1.setText("请输入数字字符");
text2.setText("请输入数字字符");
}
}
else if(e.getSource()==button2)
{
try{ number1=Double.valueOf(text1.getText()).doubleValue();
number2=Double.valueOf(text1.getText()).doubleValue();
text3.setText(""+number1-number2);
}
catch(NumberFormatException event)
{ text1.setText("请输入数字字符");
text2.setText("请输入数字字符");
}
}
else if(e.getSource()==button3)
{
try{ number1=Double.valueOf(text1.getText()).doubleValue();
number2=Double.valueOf(text1.getText()).doubleValue();
text3.setText(""+number1*number2);
}
catch(NumberFormatException event)
{ text1.setText("请输入数字字符");
text2.setText("请输入数字字符");
}
}
else if(e.getSource()==button4)
{
try{ number1=Double.valueOf(text1.getText()).doubleValue();
number2=Double.valueOf(text1.getText()).doubleValue();
text3.setText(""+number1/number2);
}
catch(NumberFormatException event)
{ text1.setText("请输入数字字符");
text2.setText("请输入数字字符");
}
}
}
}