calculate.java

java老师给的java例子很不错

import java.awt.*;
import java.awt.event.*;
public class  Calculate  extends Frame implements ActionListener
{
       Frame f;
       TextField t1;
       TextField t2;
       TextField t3;
       TextField t4;
       Label L1;
       Button btn;
       public Calculate()
       {
          Frame f=new Frame("计算器"); 
          f.setSize(300,200);    
          f.setLayout(new FlowLayout());                         
  	  t1=new TextField(5);
          t2=new TextField(5);
          t3=new TextField(5);
          t4=new TextField(5);
          L1=new Label("=");
          btn=new Button("计算");
          f.add(t1);f.add(t2);f.add(t3);f.add(t4);
          f.add(L1);f.add(btn);
          f.setVisible(true);
          btn.addActionListener(this); 
  	  f.addWindowListener(new WindowAdapter(){
                      public void windowClosing(WindowEvent e){
                       dispose();   
                       System.exit(0);
                        }
                      });	 
         }
          
        public void actionPerformed(ActionEvent e){
        float x,y;
        double result=0;
        String op;
        try{
          x=Float.parseFloat(t1.getText());
          y=Float.parseFloat(t3.getText());
          op=t2.getText();
          if(op.equals("+")) result=x+y;
          else if(op.equals("-")) result=x-y;
          else if(op.equals("*")) result=x*y;
          else if(op.equals("/")) result=x/y;
          t4.setText(Double.toString(result));
         } catch(Exception ee) {t4.setText("数据错误");}
      }
        
        public static void main(String args[])
 	{
  	       new Calculate();
 	}
}