calculator.java

来自「一个简单易懂的计算器。实现计算的一般功能。用java实现。」· Java 代码 · 共 95 行

/**
	A Simple Calculator designed by using Grid Layout 
 */

import java.awt.*;
import java.awt.event.*;
import javax.swing.*;

public class Calculator {
   public static void main(String[] args) {
   	  try {
          UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());		
      } 
      catch (Exception e) { }
    
      JFrame frame = new CalculatorFrame();
      frame.show();  
   }
}

class CalculatorPanel extends JPanel implements ActionListener {
   private JTextField display;
   private JButton btn;
   private double arg = 0;
   private String op = "=";
   private boolean start = true;
   
   public CalculatorPanel() {
      setLayout(new BorderLayout());
      
      display = new JTextField("0");
      display.setEditable(false);
      add(display, "North");
      
      JPanel p = new JPanel();
      p.setLayout(new GridLayout(4, 4));
      String buttons = "789/456*123-0.=+";
      for (int i = 0; i < buttons.length(); i++) {
      	 btn = new JButton(buttons.substring(i, i + 1));
      	 p.add(btn);
      	 btn.addActionListener(this);
      }      
      add(p, "Center");
   }
 
   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);
   }
}

class CalculatorFrame extends JFrame {
   public CalculatorFrame() {
      setTitle("Calculator");
      setSize(220, 180);
      addWindowListener(new WindowAdapter() {
          public void windowClosing(WindowEvent e) {
              System.exit(0);
          }
      });

      Container contentPane = getContentPane();
      contentPane.add(new CalculatorPanel());
   }
}