jisuan.java

java教程中的编程实例

// jisuan: Calculator
import java.awt.*;
import java.awt.event.*;
import javax.swing.*;
import java.util.*;

public class jisuan extends JApplet implements ActionListener
{
  private JTextField jtf = new JTextField(10);
  private boolean newNumber = true;
  private int result = 0;
  private String op = "=";
  Stack cunchu;
public void init()  
  {  
    //布局管理，设定按钮
    JButton bt;
    JPanel p = new JPanel();
    p.setLayout(new BorderLayout());
    cunchu=new Stack();
    JPanel westPanel = new JPanel();
    westPanel.setLayout(new GridLayout(5, 0));
    westPanel.add(new JButton("   "));
    westPanel.add(bt=new JButton("MC"));
    bt.addActionListener(this);
    westPanel.add(bt=new JButton("MR"));
     bt.addActionListener(this);
    westPanel.add(bt=new JButton("MS"));
     bt.addActionListener(this);
    westPanel.add(bt=new JButton("M+"));
     bt.addActionListener(this);

    Panel centerPanel = new Panel();
    centerPanel.setLayout(new BorderLayout());
    Panel p1 = new Panel();
    Panel p2 = new Panel();
    //设定按钮，处理事件
    p1.setLayout(new FlowLayout(FlowLayout.RIGHT));
    p1.add(bt=new JButton("Back"));
    bt.addActionListener(this);
    p1.add(bt=new JButton("CE"));
    bt.addActionListener(this);
    p1.add(bt=new JButton("C"));
    bt.addActionListener(this);
    p2.setLayout(new GridLayout(4, 5));
    p2.add(bt = new JButton("7"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("8"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("9"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("/"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("4"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("5"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("6"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("*"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("1"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("2"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("3"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("-"));
    bt.addActionListener(this);
    p2.add(bt=new JButton("0"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("%"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("+"));
    bt.addActionListener(this);
    p2.add(bt = new JButton("="));
    bt.addActionListener(this);

    centerPanel.add(p2, BorderLayout.CENTER);
    centerPanel.add(p1, BorderLayout.NORTH);
    p.add(centerPanel, BorderLayout.CENTER);
    p.add(westPanel, BorderLayout.WEST);

    getContentPane().setLayout(new BorderLayout());
    getContentPane().add(p, BorderLayout.CENTER);
    getContentPane().add(jtf, BorderLayout.NORTH);
  }

  public void actionPerformed(ActionEvent e)
  { //事件处理
    String actionCommand = e.getActionCommand();
   if(actionCommand.equals("MS"))//对MS进行操作，进栈
    {  if(!jtf.getText().equals("")) {
       while(!cunchu.empty())cunchu.pop();
        cunchu.push(jtf.getText()); 
        
         }
         }
   if(actionCommand.equals("MC"))//对MC进行操作，出栈
     {
      while(!cunchu.empty())cunchu.pop();
      }
   if(actionCommand.equals("M+"))//对M+进行操作，对栈顶元素乘2
    {
     if(!cunchu.empty())
       { 
        int abc=new Integer(cunchu.pop().toString()).intValue();
        cunchu.push(""+(2*abc));
          }
     } 
   if(actionCommand.equals("MR"))//对MR进行操作，返回栈顶元素
     {
     if(!cunchu.empty()){
     jtf.setText(cunchu.peek().toString());
      newNumber=false;
      result=new Integer(cunchu.peek().toString()).intValue();
      }
    }
  if(actionCommand.charAt(0)=='B')//对Back操作，取消上一位输入的数字
    jtf.setText(jtf.getText().substring(0,jtf.getText().length()-1));

 
  if(actionCommand.charAt(0)=='C')//对C操作，清零
    { newNumber=true;
      jtf.setText("");
      result=0;
     }
  
  else if(actionCommand.substring(0,1).equals("CE"))
//对CE操作，取消上一次输入的数字
   {  
      jtf.setText("");
      newNumber=true;
    }
     
  else   if ('0' <= actionCommand.charAt(0) &&
      actionCommand.charAt(0) <= '9')//如果输入为数字
    {
      if (newNumber)
      {
        jtf.setText(actionCommand);
        newNumber = false;
      }
      else
      {
        jtf.setText(jtf.getText() + actionCommand);
      }
    }//是否为加减乘除操作符 
    else
      if(actionCommand.length()==1 && actionCommand.charAt(0)!='C'){
      if (newNumber)
      {
        if (actionCommand.equals("-"))
        {
          jtf.setText("-");
          newNumber = false;
        }
        else
          op = actionCommand;
      }
      else
      {
        execute(); //运算操作
        op = actionCommand;
      }
    }
   }
  void execute()//运算操作
  {
    int number = new Integer(jtf.getText()).intValue();
    System.out.println("number "+op);
    switch (op.charAt(0))
    {
      case '+': result += number; break;
      case '-': result -= number; break;
      case '*': result *= number; break;
      case '/': result /= number; break;
      case '%': result %= number; break;
      case '=': result = number;
                 newNumber=false;
    }
    System.out.println("result "+result);
    jtf.setText(new Integer(result).toString());
    newNumber = true;
  }
}