calculatorpanel.java

个人财务管理的程序 很实用的

import java.util.*;
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.border.*;
import javax.swing.table.*;
//*****************************************************************
//这是一个计算器类
//*****************************************************************
class CalculatorPanel extends JPanel implements ActionListener {
   public CalculatorPanel() {
      setLayout(new BorderLayout());

      display=new JTextField("0");
      display.setBackground(Color.white);
      display.setEditable(false);
      add(display,"North");

      JPanel p=new JPanel();
      p.setLayout(new GridLayout(4,4,10,10));
      String buttons="789/456*123-0.=+";
      for(int i=0;i<buttons.length();i++)
         addButton(p,buttons.substring(i,i+1));
      add(p,"Center");
   }

   private void addButton(Container c,String s) {
      JButton button=new JButton(s);
      c.add(button);
      button.setFont(new Font("SansSerif",Font.BOLD,16));
      button.setForeground(Color.blue);
      button.setBorder(BorderFactory.createRaisedBevelBorder());
      button.addActionListener(this);
   }

   public void actionPerformed(ActionEvent evt) {
      String s=evt.getActionCommand();
      if('0'<=s.charAt(0)&&s.charAt(0)<='9'
         ||s.equals(".")) {
         if(start) display.setText(s);
         else display.setText(display.getText()+s);
         start=false;
      }
      else {
         if(start) {
            if(s.equals("-")) { display.setText(s);start=false; }
            else op=s;
         }
         else {
            double x=
               Double.parseDouble(display.getText());
            calculate(x);
            op=s;
            start=true;
         }
      }
   }

   public void calculate(double n) {
      if(op.equals("+"))  arg+=n;
      else if(op.equals("-")) arg-=n;
      else if(op.equals("*")) arg*=n;
      else if(op.equals("/")) arg/=n;
      else if(op.equals("=")) arg =n;
      display.setText(" "+arg);
   }

   private JTextField display;
   private double arg=0;
   private String op="=";
   private boolean start=true;
}