计算器应用程序

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这里写图片描述

Calculator.java

package webstart;import java.awt.*;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);            }         });   }}

CalculatorFrame.java

package webstart;import java.awt.event.*;import java.beans.*;import java.io.*;import java.net.*;import javax.jnlp.*;import javax.swing.*;/** * A frame with a calculator panel and a menu to load and save the calculator history. */public class CalculatorFrame extends JFrame{   private CalculatorPanel panel;   public CalculatorFrame()   {      setTitle();      panel = new CalculatorPanel();      add(panel);      JMenu fileMenu = new JMenu("File");      JMenuBar menuBar = new JMenuBar();      menuBar.add(fileMenu);      setJMenuBar(menuBar);      JMenuItem openItem = fileMenu.add("Open");      openItem.addActionListener(EventHandler.create(ActionListener.class, this, "open"));      JMenuItem saveItem = fileMenu.add("Save");      saveItem.addActionListener(EventHandler.create(ActionListener.class, this, "save"));      pack();   }   /**    * Gets the title from the persistent store or asks the user for the title if there is no prior    * entry.    */   public void setTitle()   {      try      {         String title = null;         BasicService basic = (BasicService) ServiceManager.lookup("javax.jnlp.BasicService");         URL codeBase = basic.getCodeBase();         PersistenceService service = (PersistenceService) ServiceManager               .lookup("javax.jnlp.PersistenceService");         URL key = new URL(codeBase, "title");         try         {            FileContents contents = service.get(key);            InputStream in = contents.getInputStream();            BufferedReader reader = new BufferedReader(new InputStreamReader(in));            title = reader.readLine();         }         catch (FileNotFoundException e)         {            title = JOptionPane.showInputDialog("Please supply a frame title:");            if (title == null) return;            service.create(key, 100);            FileContents contents = service.get(key);            OutputStream out = contents.getOutputStream(true);            PrintStream printOut = new PrintStream(out);            printOut.print(title);         }         setTitle(title);      }      catch (UnavailableServiceException e)      {         JOptionPane.showMessageDialog(this, e);      }      catch (MalformedURLException e)      {         JOptionPane.showMessageDialog(this, e);      }      catch (IOException e)      {         JOptionPane.showMessageDialog(this, e);      }   }   /**    * Opens a history file and updates the display.    */   public void open()   {      try      {         FileOpenService service = (FileOpenService) ServiceManager               .lookup("javax.jnlp.FileOpenService");         FileContents contents = service.openFileDialog(".", new String[] { "txt" });         JOptionPane.showMessageDialog(this, contents.getName());         if (contents != null)         {            InputStream in = contents.getInputStream();            BufferedReader reader = new BufferedReader(new InputStreamReader(in));            String line;            while ((line = reader.readLine()) != null)            {               panel.append(line);               panel.append("\n");            }         }      }      catch (UnavailableServiceException e)      {         JOptionPane.showMessageDialog(this, e);      }      catch (IOException e)      {         JOptionPane.showMessageDialog(this, e);      }   }   /**    * Saves the calculator history to a file.    */   public void save()   {      try      {         ByteArrayOutputStream out = new ByteArrayOutputStream();         PrintStream printOut = new PrintStream(out);         printOut.print(panel.getText());         InputStream data = new ByteArrayInputStream(out.toByteArray());         FileSaveService service = (FileSaveService) ServiceManager               .lookup("javax.jnlp.FileSaveService");         service.saveFileDialog(".", new String[] { "txt" }, data, "calc.txt");      }      catch (UnavailableServiceException e)      {         JOptionPane.showMessageDialog(this, e);      }      catch (IOException e)      {         JOptionPane.showMessageDialog(this, e);      }   }}

CalculatorPanel.java

package webstart;import java.awt.*;import java.awt.event.*;import javax.swing.*;import javax.swing.text.*;/**   A panel with calculator buttons and a result display.*/public class CalculatorPanel extends JPanel{     private JTextArea display;   private JPanel panel;   private double result;   private String lastCommand;   private boolean start;   /**      Lays out the panel.   */   public CalculatorPanel()   {        setLayout(new BorderLayout());      result = 0;      lastCommand = "=";      start = true;      // add the display      display = new JTextArea(10, 20);      add(new JScrollPane(display), BorderLayout.NORTH);      ActionListener insert = new InsertAction();      ActionListener command = new CommandAction();      // add the buttons in a 4 x 4 grid      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);   }   /**      Gets the history text.      @return the calculator history   */   public String getText()   {      return display.getText();   }   /**      Appends a string to the history text.      @param s the string to append   */   public void append(String s)   {      display.append(s);   }   /**      Adds a button to the center panel.      @param label the button label      @param listener the button listener   */   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();         start = false;         display.append(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.append(command);                start = false;             }            else                lastCommand = command;         }         else         {              try            {               int lines = display.getLineCount();               int lineStart = display.getLineStartOffset(lines - 1);               int lineEnd = display.getLineEndOffset(lines - 1);               String value = display.getText(lineStart, lineEnd - lineStart);               display.append(" ");               display.append(command);                calculate(Double.parseDouble(value));               if (command.equals("="))                  display.append("\n" + result);               lastCommand = command;               display.append("\n");               start = true;            }            catch (BadLocationException e)            {               e.printStackTrace();            }         }      }   }   /**      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;   }  }

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