corejava/corejava第9版/v1ch11/except/ExceptTest.java

package except;

import java.awt.EventQueue;
import java.awt.event.*;
import java.io.*;
import java.nio.file.*;
import java.util.*;
import javax.swing.*;

/**
 * @version 1.33 2007-06-12
 * @author Cay Horstmann
 */
public class ExceptTest
{
   public static void main(String[] args)
   {
      EventQueue.invokeLater(new Runnable()
         {
            public void run()
            {
               JFrame frame = new ExceptTestFrame();
               frame.setTitle("ExceptTest");   
               frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
               frame.setVisible(true);
            }
         });
   }
}

/**
 * A frame with a panel for testing various exceptions
 */
class ExceptTestFrame extends JFrame
{
   public ExceptTestFrame()
   {
      ExceptTestPanel panel = new ExceptTestPanel();
      add(panel);
      pack();
   }
}

/**
 * A panel with radio buttons for running code snippets and studying their exception behavior
 */
class ExceptTestPanel extends Box
{
   private ButtonGroup group;
   private JTextField textField;
   private double[] a = new double[10];

   public ExceptTestPanel()
   {
      super(BoxLayout.Y_AXIS);
      group = new ButtonGroup();

      // add radio buttons for code snippets

      addRadioButton("Integer divide by zero", new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               a[1] = 1 / (a.length - a.length);
            }
         });

      addRadioButton("Floating point divide by zero", new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               a[1] = a[2] / (a[3] - a[3]);
            }
         });

      addRadioButton("Array bounds", new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               a[1] = a[10];
            }
         });

      addRadioButton("Bad cast", new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               a = (double[]) event.getSource();
            }
         });

      addRadioButton("Null pointer", new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               System.out.println(textField.getAction().toString());
            }
         });

      addRadioButton("sqrt(-1)", new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               a[1] = Math.sqrt(-1);
            }
         });

      addRadioButton("Overflow", new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               a[1] = 1000 * 1000 * 1000 * 1000;
               int n = (int) a[1];
               System.out.println(n);
            }
         });

      addRadioButton("No such file", new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               try
               {
                  System.out.println(new Scanner(Paths.get("woozle.txt")).next());
               }
               catch (IOException e)
               {
                  textField.setText(e.toString());
               }
            }
         });

      addRadioButton("Throw unknown", new ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {
               throw new UnknownError();
            }
         });

      // add the text field for exception display
      textField = new JTextField(30);
      add(textField);
   }

   /**
    * Adds a radio button with a given listener to the panel. Traps any exceptions in the
    * actionPerformed method of the listener.
    * @param s the label of the radio button
    * @param listener the action listener for the radio button
    */
   private void addRadioButton(String s, ActionListener listener)
   {
      JRadioButton button = new JRadioButton(s, false)
         {
            // the button calls this method to fire an
            // action event. We override it to trap exceptions
            protected void fireActionPerformed(ActionEvent event)
            {
               try
               {
                  textField.setText("No exception");
                  super.fireActionPerformed(event);
               }
               catch (Exception e)
               {
                  textField.setText(e.toString());
               }
            }
         };

      button.addActionListener(listener);
      add(button);
      group.add(button);
   }
}