java 简单的计算器程序实例代码

java 简单的计算器程序

实现实例：

import java.awt.*; 
import java.awt.event.*; 
import javax.swing.*; 
 
 
public class calculator 
{ 
  public static void main(string[] args) 
  { 
   eventqueue.invokelater(new runnable() 
     { 
      public void run() 
      { 
        calculatorframe frame = new calculatorframe(); 
        frame.setdefaultcloseoperation(jframe.exit_on_close); 
        frame.setvisible(true); 
      } 
     }); 
  } 
} 
 
 
/** 
 * a frame with a calculator panel. 
 */ 
class calculatorframe extends jframe 
{ 
  public calculatorframe() 
  { 
    settitle("calculator"); 
    calculatorpanel panel=new calculatorpanel(); 
    add(panel); 
    pack(); 
  } 
} 
 
 
class calculatorpanel extends jpanel 
{ 
  private jbutton display; 
    private jpanel panel; 
    private double result; 
    private string lastcommand; 
    private boolean start; 
  public calculatorpanel() 
  { 
    setlayout(new borderlayout()); 
     
    result=0; 
    lastcommand="="; 
    start=true; 
     
     // add the display 
    display=new jbutton("0"); 
    display.setenabled(false); 
    add(display,borderlayout.north); 
     
    actionlistener insert=new insertaction(); 
    actionlistener command=new commandaction(); 
     
    panel=new jpanel(); 
    panel.setlayout(new gridlayout(4,4)); 
     
     addbutton("7", insert); 
     addbutton("8", insert); 
     addbutton("9", insert); 
     addbutton("/", command); 
 
 
     addbutton("4", insert); 
     addbutton("5", insert); 
     addbutton("6", insert); 
     addbutton("*", command); 
 
 
     addbutton("1", insert); 
     addbutton("2", insert); 
     addbutton("3", insert); 
     addbutton("-", command); 
 
 
     addbutton("0", insert); 
     addbutton(".", insert); 
     addbutton("=", command); 
     addbutton("+", command); 
 
 
     add(panel, borderlayout.center); 
     
    } 
  private void addbutton(string label,actionlistener listener) 
  { 
    jbutton button=new jbutton(label); 
    button.addactionlistener(listener); 
    panel.add(button); 
  } 
  /** 
    * this action inserts the button action string to the end of the display text. 
    */ 
  private class insertaction implements actionlistener 
  { 
    public void actionperformed(actionevent event) 
    { 
      string input=event.getactioncommand(); 
      if(start) 
      { 
        display.settext(""); 
        start=false; 
      } 
      display.settext(display.gettext()+input); 
    } 
  } 
   /** 
    * this action executes the command that the button action string denotes. 
    */ 
  private class commandaction implements actionlistener 
  { 
    public void actionperformed(actionevent event) 
    { 
      string command=event.getactioncommand(); 
      if(start) 
      { 
        if (command.equals("-")) 
        { 
          display.settext(command); 
          start = false; 
        } 
        else lastcommand = command; 
      }else { 
        calculate(double.parsedouble(display.gettext())); 
        lastcommand=command; 
        start=true; 
      } 
    } 
  } 
  /** 
    * carries out the pending calculation. 
    * @param x the value to be accumulated with the prior result. 
    */ 
  public void calculate(double x) 
  { 
     if (lastcommand.equals("+")) result += x; 
     else if (lastcommand.equals("-")) result -= x; 
     else if (lastcommand.equals("*")) result *= x; 
     else if (lastcommand.equals("/")) result /= x; 
     else if (lastcommand.equals("=")) result = x; 
     display.settext("" + result); 
  } 
} 

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