classbrowsertest.java

这个是我老师给的关于Java核心技术2的第6章的源代码

/**
   @version 1.02 2004-08-21
   @author Cay Horstmann
*/

import java.awt.*;
import java.awt.event.*;
import java.lang.reflect.*;
import java.util.*;
import javax.swing.*;
import javax.swing.event.*;
import javax.swing.tree.*;

/**
   This program demonstrates tree selection events.
*/
public class ClassBrowserTest
{  
   public static void main(String[] args)
   {  
      JFrame frame = new ClassBrowserTestFrame();
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      frame.setVisible(true);
   }
}

/**
   A frame with a class tree, a text area to show the properties
   of the selected class, and a text field to add new classes.
*/
class ClassBrowserTestFrame extends JFrame
{  
   public ClassBrowserTestFrame()
   {  
      setTitle("ClassBrowserTest");
      setSize(DEFAULT_WIDTH, DEFAULT_HEIGHT);

      // the root of the class tree is Object
      root = new DefaultMutableTreeNode(java.lang.Object.class);
      model = new DefaultTreeModel(root);
      tree = new JTree(model);

      // add this class to populate the tree with some data
      addClass(getClass());

      // set up selection mode
      tree.addTreeSelectionListener(new
         TreeSelectionListener()
         {
            public void valueChanged(TreeSelectionEvent event)
            {  
               // the user selected a different node--update description
               TreePath path = tree.getSelectionPath();
               if (path == null) return;
               DefaultMutableTreeNode selectedNode 
                  = (DefaultMutableTreeNode) path.getLastPathComponent();
               Class c = (Class) selectedNode.getUserObject();
               String description = getFieldDescription(c);
               textArea.setText(description);
            }
         });
      int mode = TreeSelectionModel.SINGLE_TREE_SELECTION;
      tree.getSelectionModel().setSelectionMode(mode);

      // this text area holds the class description
      textArea = new JTextArea();

      // add tree and text area 
      JPanel panel = new JPanel();
      panel.setLayout(new GridLayout(1, 2));
      panel.add(new JScrollPane(tree));
      panel.add(new JScrollPane(textArea));

      add(panel, BorderLayout.CENTER);

      addTextField();
   }

   /**
      Add the text field and "Add" button to add a new class.
   */
   public void addTextField()
   {
      JPanel panel = new JPanel();

      ActionListener addListener = new
         ActionListener()
         {
            public void actionPerformed(ActionEvent event)
            {  
               // add the class whose name is in the text field
               try
               {  
                  String text = textField.getText();
                  addClass(Class.forName(text));
                  // clear text field to indicate success
                  textField.setText("");
               }
               catch (ClassNotFoundException e)
               {  
                  JOptionPane.showMessageDialog(null, "Class not found");
               }
            }
         };

      // new class names are typed into this text field
      textField = new JTextField(20);
      textField.addActionListener(addListener);
      panel.add(textField);

      JButton addButton = new JButton("Add");
      addButton.addActionListener(addListener);
      panel.add(addButton);

      add(panel, BorderLayout.SOUTH);
   }

   /**
      Finds an object in the tree.
      @param obj the object to find
      @return the node containing the object or null
      if the object is not present in the tree
   */
   public DefaultMutableTreeNode findUserObject(Object obj)
   {  
      // find the node containing a user object
      Enumeration e = root.breadthFirstEnumeration();
      while (e.hasMoreElements())
      {  
         DefaultMutableTreeNode node = (DefaultMutableTreeNode) e.nextElement();
         if (node.getUserObject().equals(obj))
            return node;
      }
      return null;
   }

   /**
      Adds a new class and any parent classes that aren't
      yet part of the tree
      @param c the class to add
      @return the newly added node.
   */
   public DefaultMutableTreeNode addClass(Class c)
   {  
      // add a new class to the tree

      // skip non-class types
      if (c.isInterface() || c.isPrimitive()) return null;

      // if the class is already in the tree, return its node
      DefaultMutableTreeNode node = findUserObject(c);
      if (node != null) return node;

      // class isn't present--first add class parent recursively

      Class s = c.getSuperclass();

      DefaultMutableTreeNode parent;
      if (s == null)
         parent = root;
      else
         parent = addClass(s);

      // add the class as a child to the parent
      DefaultMutableTreeNode newNode = new DefaultMutableTreeNode(c);
      model.insertNodeInto(newNode, parent, parent.getChildCount());

      // make node visible
      TreePath path = new TreePath(model.getPathToRoot(newNode));
      tree.makeVisible(path);

      return newNode;
   }

   /**
      Returns a description of the fields of a class.
      @param the class to be described
      @return a string containing all field types and names 
   */
   public static String getFieldDescription(Class c)
   {  
      // use reflection to find types and names of fields
      StringBuilder r = new StringBuilder();
      Field[] fields = c.getDeclaredFields();
      for (int i = 0; i < fields.length; i++)
      {  
         Field f = fields[i];
         if ((f.getModifiers() & Modifier.STATIC) != 0) r.append("static ");
         r.append(f.getType().getName());
         r.append(" ");
         r.append(f.getName());
         r.append("\n");
      }
      return r.toString();
   }

   private DefaultMutableTreeNode root;
   private DefaultTreeModel model;
   private JTree tree;
   private JTextField textField;
   private JTextArea textArea;
   private static final int DEFAULT_WIDTH = 400;
   private static final int DEFAULT_HEIGHT = 300;
}