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This column discusses property editors and how to implement one for Java -specifically, how to make one work for our CodeDocument class. When last we talked, we saw how to build a CodeDocument class, but it wasn't something we could work with in a visual designer like JBuilder, say, or Visual Cafe. In this column we'll build a special case of the JTextArea component and add some specialty properties and property editors to support the CodeDocument class we worked on before. The code listings at the end of the article are excerpted from the complete code, which you can download from www.JavaDevelopersJournal.com.

Property Editors and How They Work
Basically, property editors allow you to edit a property. Wow! What a concept! Except that to make this work the IDE has to know what the property is. Luckily, since we're talking about Java, we have a neat little tool called Reflection that we can use to ask any given object, "What are you?" and get back a response like, "I'm a java.lang.String class object." Great, now we know what we're dealing with...but wait a minute...hold the bus. How do we know how to edit the object? "It's a string. How hard can it be?" you say. Well, if everything were a string, we'd have no problems, but things are a little more complicated than that. Granted, a string is easy to edit, but what about a color object, or a collection of items (like a vector)? Since a property can be any kind of object, we need to have a uniform way of explaining to the IDE how to edit that object, and, if necessary, supply a custom UI with which to edit the property. So the property editor interface provides just the thing we need, with methods to get and set the object in question, as well as methods for telling whether the property editor supports a custom UI editor.

Property editors by themselves don't do much good. For the IDE to "know" about them, the component whose properties we're interested in must publish BeanInfo.

The BeanInfo interface describes the component to the IDE with information such as the icon to display as a visual representation of the component and - you guessed it -a list of property descriptors. What do the property descriptors do? They describe properties! Each property descriptor contains information such as the name of the get and set methods, the name of the property, the class the property belongs to and, finally (and this is optional), the PropertyEditor class itself. Thus, when the user asks to edit a property, the IDE first retrieves the component's BeanInfo class and then the property descriptor for the desired property. If the property descriptor supports a custom editor, the custom editor is then loaded and the custom editor component is loaded and displayed for the user to work with (this usually takes place in a dialog of some sort -at least this is how JBuilder handles things).

Adding Our Own Property Editor for the CodeDocument
Let's take this knowledge and do something practical with it. Let's add a new component based on JTextPane, which automatically uses a Document model based on our CodeDocument class. We'll start with the code shown in Listing 1.

All right, that was pretty painless. What we're doing is calling the super class in the constructor and setting the document to a new instance of the CodeDocument class we developed previously. We're going to add a single property -call keywords -that will allow the developer to modify the CodeDocument keywords attribute. Doing this changes the set of keywords the CodeDocument looks for in its syntax highlighting process. Let's look at another example demonstrating this, in Listing 2.

So now we've added two methods that allow us to get and set keywords. We overloaded the setKeywords method to allow for either a vector of keywords or an array of strings (the array of string method simply converts the array to a vector and calls the vector version of the method).

This will become more important when we add our property editor later on. Notice that we didn't add an attribute of type Vector to the code -we're simply mapping any calls to get or set keywords directly back to the CodeDocument class. Now we have our component, and if we wanted to we could leave it at that. However, we wouldn't have a property editor working yet, thus defeating the point of this article!

The next thing we need to add is the BeanInfo class. BeanInfo is actually an interface that you need to implement in some other class to make things work. So let's create our BeanInfo implementation class, as seen in Listing 3.

So far this is pretty basic. As mentioned before, the BeanInfo methods allow an IDE to determine all sorts of information about the component and the properties it supports. In our implementation you'll notice we extend SimpleBeanInfo, a class that has all the methods of the BeanInfo stubbed out. Since there are a few other methods that aren't neccessary for us at this point, extending SimpleBeanInfo makes our life a little easier, allowing us to focus on just the parts we need. As mentioned earlier, getPropertyDescriptors() is the method called by the IDE to get all the property info. We'll return an array of property descriptors only for the properties we're interested in exposing to the IDE for user manipulation. In our case there will be only one element, for the keywords property. The getIcon() method will return either null or an image containing a 16x16 icon (black and white or color) that represents the component or a 32x32 icon (also black and white or color). The kind of icon is determined by the iconKind parameter passed into the method (the choices are ICON_COLOR_16x16, ICON_COLOR_32x32, ICON_MONO_16x16, and ICON_MONO_32x32). The getAdditionalBeanInfo() is supposed to call the super class and request more bean info from that class.

For now, let's look at the getPropertyDescriptors() method. In our implementation we need to supply only one element in the array. We don't need to worry about any of the super class properties. If we had another property that was a string -say, DocumentName -we wouldn't have to worry about it either. Why? Because objects like string and integer almost always have default property editors registered in the IDE and there's usually no need to register something else. But let's say that, instead of DocumentName, our property was called FileName, and we wanted to bring up some kind of file open dialog when the user tried to edit it. Now we'd want to supply a custom property editor for the string, causing a file open dialog to pop up when the property is edited. Back to our implementation. To set up the element properly, let's look at Listing 4.

The first thing we do is create a new instance of a PropertyDescriptor class by passing in the name of the property, the class it belongs to (in our case CodeTextPane) and the names of the get and set methods. The setDisplayName() method is used to define the text that will be displayed for your property, and the setShortDescription is used to populate tool tips with a short description of your property. The setPropertyEditorClass() method is used to set the class type for your property editor. It's important to set this up correctly; otherwise the property editor won't be picked up by the IDE. The class KeywordsEditor is the one we're going to create next, in case you're wondering where it came from. After this is done we'll create a new array of PropertyDescriptor objects (the propertyDescriptors variable) and put the new instance we created previously into the array. Then we just return the array.

The only other method we'll bother implementing in our implementation of BeanInfo is the getAdditionalBeanInfo() method. This is given in Listing 5.

By providing additional BeanInfo, we're giving the IDE more information about our object -specifically, about the object's super class. Similar to the PropertyDescriptor, we're returning an array of objects, each a reference to BeanInfo. In our implementation we call the Introspector's getBeanInfo() method to get the super class's bean info.

So far we've gone through all the steps neccessary to create a simple component (CodeTextPane) and supply an implementation of BeanInfo that properly exposes our property (keywords) and its custom editor class (KeywordsEditor). Now it's time to look at the property editor class directly. The class will actually have two parts: the first is the property editor class itself, KeywordsEditor (Listing 6a); the second is the custom editor component, KeywordsEditorComponent (Listing 6b).

The property editor interface is fairly easy to implement, especially when we extend from the PropertyEditorSupport class. Like the SimpleBeanInfo, it provides either stubs or simple implementations of the methods so we can concentrate on the few that are important to us. Since we want to support a custom editor component, we return true from the supportsCustomEditor() method that's called by the IDE. We also return an instance of our editor component in the getCustomEditor() method. Since getCustomEditor() returns a component, we can base our editor component on practically anything. Usually the component gets nested into some other container, like a dialog (this is the case with JBuilder), so basing it on JPanel is usually a good idea. The getJavaInitializationString() method returns a string that represents the Java code required to set the given property from the code editor. Whenever you change the property via your custom editor, this string will need to change as well. An example would be a property that is a font object. In your IDE's code editor, you might see something like this:

public void myInitMethod(){
//more code
this.setFont(new Font("SansSerif", 1, 12));
//more code...
}

The line "new Font("SansSerif", 1, 12)" would be provided to the IDE by whatever property editor is registered for the font property of the object. This string would be the return of the property editor's getJavaInitializationString() method. In our case the string might look like the following:

public void myInitMethod(){
//more code
codeTextPaneObj.setKeywords(new String[]{"foo","bar","blah",});
//more code...
}

Since there's no convenient way to represent a vector like this, we can use our second version of the setKeywords() method to pass in the new set of keywords. The implementation code for the getJavaInitializationString() method would look like Listing 7.

The getValue() method returns the current value of the property represented by the property editor (it's already implemented for us by the PropertyEditorSupport class). We then go through all the elements in the vector and assemble them into a string, returning this string when we're finished.

With this done we have our PropertyEditor class ready to go. Now we can take a look at designing the custom editor component. For starters let's take a look again at Listing 6b. The class is simple. It extends Panel (or JPanel if you want to have a Swing look) and has a constructor that takes one argument -a property editor object that's set to a private variable.

As it stands, the component will do absolutely nothing, so let's add a listbox to view all our keywords, an edit box to type in new keywords, two labels -one for the list and one for the edit box -and, finally, two buttons -one to add the information in the edit box and one to delete selected items from the keywords list. Take a look at Listing 8.

The keywords variable is a DefaultListModel, Swing's default implementation of a suitable list model for use in JList controls. So when we add items to the list, we don't bother calling the control methods; instead, we actually manipulate the keywords object. The JList is constructed by passing in the keywords object as its model, so everything is hooked up for us. The next thing we need to add is a private initialization method to set all the widget properties and hook up event listeners, as well as to configure a GridBagLayout to position all the controls properly. We'll call this method initEditor(), and instead of showing all the code here (you can see it on the JDJ Web site), I'm just going to present the sections relevant to the article. The main thing we need to catch are changes to the keywords list. Each time it changes, we need to call the property editor's setValue() method to inform it of a change, which in turn notifies any registered listeners that the property has changed. That way, when our editor component is dismissed, the property is in a valid state and the getJavaInitializationString() will return correct data. To accomplish this we register a listener with the keywords object as seen in Listing 9 (this takes place in the initEditor() method).

This ensures that any change to the keywords object will call the keywords_changed() method (a private method of the editor component), which properly updates the property editor. According to the Java documentation, you shouldn't actually modify the property editor value directly; instead, you should just send a new instance. To do that we end up with the code in Listing 10.

The method simply makes a copy of the elements in the keywords list and places them in a new instance of a vector that can then be sent to the property editor via the setValue() method.

One other thing of interest in the initEditor() method is the setting of the listbox to the current value of the property editor. This is accomplished in Listing 11.

The keywords object is cleared using the removeAll() method, and the property editor's value is retrieved through the getValue() method and then enumerated; the new elements are then added to the keywords list.

That's It, Folks!
We're done!

  • We've covered creating a new text component with support for our previously created CodeDocument class.
  • We've created a BeanInfo class to ensure that IDEs such as JBuilder are aware of the properties we're exposing and any custom features, like editors, we support.
  • We've created a property editor class to support our new property.
  • We've created a custom editor component that will allow us to edit that property in a visual way.
Whew! I hope this was helpful -let me know how it works for you by e-mailing me at [email protected]

Author Bio
Jim Crafton is part of the R&D team at Improv Technologies (www.improv-tech.com), helping to develop a new production-quality animation tool. In his spare time he develops advanced graphics software (you can see it at www.diegoware.com).
He can be reached at: [email protected]

	

Listing 1: 

package CodeEditor; 

import com.sun.java.swing.*; 
import com.sun.java.swing.text.*; 
import java.util.*; 
import java.awt.*; 
import java.awt.event.*; 
import java.io.*; 

public class CodeTextPane extends JTextPane implements Serializable{ 
  public CodeTextPane() { 

  } 

  void readObject(ObjectInputStream ois) throws ClassNotFoundException, IOException { 
    ois.defaultReadObject(); 
  } 

  void writeObject(ObjectOutputStream oos) throws IOException { 
    oos.defaultWriteObject(); 
  } 

  public void setKeywords(Vector aNewSetOfKeywords) { 
    Document doc = getDocument(); 
    if (doc instanceof CodeDocument) { 
      CodeDocument codeDoc = (CodeDocument) doc; 
      codeDoc.setKeywords(aNewSetOfKeywords); 
    } 
  } 

  public void setKeywords(String aNewSetOfKeywords[]){ 
    Vector v = new Vector(); 
    for (int i=0;i< aNewSetOfKeywords.length;i++){ 
      v.addElement(aNewSetOfKeywords[i]); 
    } 
    setKeywords(v); 
  } 
  

  public Vector getKeywords() { 
    Vector keywords = null; 

    Document doc = getDocument(); 
    if (doc instanceof CodeDocument) { 
      CodeDocument codeDoc = (CodeDocument) doc; 
      keywords = codeDoc.getKeywords(); 
    } 

    return keywords; 
  } 

} 
  

Listing 2: 

//Title:        Your Product Name 
//Version: 
//Copyright:    Copyright (c) 1998 
//Author:       Your Name 
//Company:      Your Company 
//Description:  Your description 

package CodeEditor; 

import java.beans.*; 

public class CodeTextPaneBeanInfo extends SimpleBeanInfo { 
  Class beanClass = CodeTextPane.class; 
  String iconColor16x16Filename; 
  String iconColor32x32Filename; 
  String iconMono16x16Filename; 
  String iconMono32x32Filename; 
  

  public CodeTextPaneBeanInfo() { 
  } 

  public PropertyDescriptor[] getPropertyDescriptors() { 
    try  { 
      PropertyDescriptor _keywords = new PropertyDescriptor("keywords", beanClass,
	   "getKeywords", "setKeywords"); 
      _keywords.setDisplayName("keywords"); 
      _keywords.setShortDescription("keywords"); 
      _keywords.setPropertyEditorClass(CodeEditor.KeywordsEditor.class); 

      PropertyDescriptor[] pds = new PropertyDescriptor[] { 
        _keywords, 
      }; 
      return pds; 
    } 
    catch (IntrospectionException ex) { 
      ex.printStackTrace(); 
      return null; 
    } 
  } 

  public java.awt.Image getIcon(int iconKind) { 
    switch (iconKind) { 
    case BeanInfo.ICON_COLOR_16x16: 
      return iconColor16x16Filename != null ? loadImage(iconColor16x16Filename) : null; 
    case BeanInfo.ICON_COLOR_32x32: 
      return iconColor32x32Filename != null ? loadImage(iconColor32x32Filename) : null; 
    case BeanInfo.ICON_MONO_16x16: 
      return iconMono16x16Filename != null ? loadImage(iconMono16x16Filename) : null; 
    case BeanInfo.ICON_MONO_32x32: 
      return iconMono32x32Filename != null ? loadImage(iconMono32x32Filename) : null; 
    } 
    return null; 
  } 

  public BeanInfo[] getAdditionalBeanInfo() { 
    Class superclass = beanClass.getSuperclass(); 
    try  { 
      BeanInfo superBeanInfo = Introspector.getBeanInfo(superclass); 
      return new BeanInfo[] { superBeanInfo }; 
    } 
    catch (IntrospectionException ex) { 
      ex.printStackTrace(); 
      return null; 
    } 
  } 
} 

Listing 3: 

//Title:        Your Product Name 
//Version: 
//Copyright:    Copyright (c) 1998 
//Author:       Your Name 
//Company:      Your Company 
//Description:  Your description 

package CodeEditor; 

import java.awt.*; 
import java.beans.*; 
import java.util.*; 

public class KeywordsEditor extends PropertyEditorSupport { 
  private KeywordsEditorComponent editor; 
  

  public KeywordsEditor() { 
  } 

  public boolean supportsCustomEditor() { 
    return true; 
  } 

  public Component getCustomEditor() { 
    if (editor == null) { 
      editor = new KeywordsEditorComponent(this); 
    } 
    return editor; 
  } 

  public String getJavaInitializationString() { 
    //TODO: Implement this for your property type 
    Vector v = (Vector)getValue(); 
    String s = "new String[] {"; 
    Enumeration enum = v.elements(); 
    while (enum.hasMoreElements()){ 
      String keyword = (String)enum.nextElement(); 
      if ( enum.hasMoreElements() ){ 
        s += "\"" + keyword + "\","; 
      } 
      else{ 
        s += "\"" + keyword + "\"}"; 
      } 
    } 
    return s; 
  } 
} 

Listing 4:
 
//Title:        Your Product Name 
//Version: 
//Copyright:    Copyright (c) 1998 
//Author:       Your Name 
//Company:      Your Company 
//Description:  Your description 

package CodeEditor; 

import java.awt.*; 
import java.awt.event.*; 
import java.beans.*; 
import com.sun.java.swing.*; 
import com.sun.java.swing.event.*; 
import java.util.*; 

public class KeywordsEditorComponent extends Panel{ 
  private PropertyEditor editor; 
  JLabel label1 = new JLabel(); 
  JLabel label2 = new JLabel(); 
  DefaultListModel keywords = new DefaultListModel(); 
  JList keywordList = new JList(keywords); 
  JTextField keywordEdit = new JTextField(); 
  JButton addBtn = new JButton(); 
  JButton deleteBtn = new JButton(); 
  JScrollPane listScroller = new JScrollPane(keywordList); 

  private void initEditor(){ 
    addBtn.setText("Add to keywords list"); 
    addBtn.addActionListener(new java.awt.event.ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
        addBtn_actionPerformed(e); 
      } 
    }); 

    deleteBtn.setText("Delete item from list"); 
    deleteBtn.addActionListener(new java.awt.event.ActionListener() { 
      public void actionPerformed(ActionEvent e) { 
        deleteBtn_actionPerformed(e); 
      } 
    }); 

    label1.setText("Keywords List"); 
    label2.setText("Keyword: "); 

    keywordEdit.setText(""); 
    keywordEdit.setPreferredSize(new Dimension(80, 25)); 

    listScroller.setPreferredSize(new Dimension(150, 200)); 

    if (editor != null){ 
      keywords.removeAllElements(); 
      Vector v = (Vector)editor.getValue(); 
      Enumeration enum = v.elements(); 
      while (enum.hasMoreElements()){ 
        keywords.addElement(enum.nextElement()); 
      } 
    } 
    keywords.addListDataListener(new ListDataListener(){ 
      public void contentsChanged(ListDataEvent e){ 
        keywords_changed(e); 
      } 
      public void intervalAdded(ListDataEvent e){ 
        keywords_changed(e); 
      } 

      public void intervalRemoved(ListDataEvent e){ 
        keywords_changed(e); 
      } 
    }); 

    //set the layout manager 
    GridBagLayout gb = new GridBagLayout(); 
    this.setLayout(gb); 
    GridBagConstraints gridConst = new GridBagConstraints(); 
    gridConst.gridx = 0; 
    gridConst.gridy = 0; 
    gridConst.gridheight = 1; 
    gridConst.gridwidth = 1; 
    gridConst.anchor = GridBagConstraints.NORTHWEST; 
    gb.setConstraints(label1,gridConst); 
    this.add(label1); 

    gridConst = new GridBagConstraints(); 
    gridConst.gridx = 0; 
    gridConst.gridy = 1; 
    gridConst.gridheight = 3; 
    gridConst.gridwidth = 2; 
    gridConst.anchor = GridBagConstraints.NORTHWEST; 
    gb.setConstraints(listScroller,gridConst); 
    this.add(listScroller); 

    gridConst = new GridBagConstraints(); 
    gridConst.gridx = 2; 
    gridConst.gridy = 0; 
    gridConst.gridheight = 1; 
    gridConst.gridwidth = 1; 
    gridConst.anchor = GridBagConstraints.NORTHEAST; 
    gb.setConstraints(label2,gridConst); 
    this.add(label2); 

    gridConst = new GridBagConstraints(); 
    gridConst.gridx = 1; 
    gridConst.gridy = 1; 
    gridConst.gridheight = 1; 
    gridConst.gridwidth = 2; 
    gridConst.anchor = GridBagConstraints.NORTHEAST; 
    gb.setConstraints(keywordEdit,gridConst); 
    this.add(keywordEdit); 

    gridConst = new GridBagConstraints(); 
    gridConst.gridx = 2; 
    gridConst.gridy = 3; 
    gridConst.gridheight = 1; 
    gridConst.gridwidth = 1; 
    gridConst.anchor = GridBagConstraints.SOUTHEAST; 
    gb.setConstraints(addBtn,gridConst); 
    this.add(addBtn); 

    gridConst = new GridBagConstraints(); 
    gridConst.gridx = 2; 
    gridConst.gridy = 4; 
    gridConst.gridheight = 1; 
    gridConst.gridwidth = 1; 
    gridConst.anchor = GridBagConstraints.SOUTHEAST; 
    gb.setConstraints(deleteBtn,gridConst); 
    this.add(deleteBtn); 
  } 

  public KeywordsEditorComponent(PropertyEditor editor) { 
    this.editor = editor; 
    initEditor(); 
  } 

  private void addBtn_actionPerformed(ActionEvent e) { 
    keywords.addElement(keywordEdit.getText()); 
  } 

  private void deleteBtn_actionPerformed(ActionEvent e) { 
    Object selectedObj = this.keywordList.getSelectedValue(); 
    if (selectedObj != null){ 
      keywords.remove(keywordList.getSelectedIndex()); 
    } 
  } 

  private void keywords_changed(ListDataEvent e){ 
    if (editor != null){ 
      Vector v = new Vector(); 
      Enumeration enum = keywords.elements(); 
      while (enum.hasMoreElements()){ 
        v.addElement(enum.nextElement()); 
      } 
      editor.setValue(v); 
    } 
  } 

} 

Listing 5:
 
package CodeEditor; 

public class ClassElement { 
  private String displayValue = ""; 
  private String elementValue = ""; 
  public ClassElement() { 
  } 

  public ClassElement(String displayText, String elementText) { 
    elementValue = elementText; 
    displayValue = displayText; 
  } 

  public String getDisplayValue(){ 
    return displayValue; 
  } 

  public String getElementValue(){ 
    return elementValue; 
  } 

  public void setElementValue(String aValue){ 
    this.elementValue = aValue; 
  } 

  public void setDisplayValue(String aValue){ 
    this.displayValue = aValue; 
  } 

  public String toString(){ 
    return displayValue; 
  } 
} 

Listing 6
 
package CodeEditor; 
import java.util.*; 
import java.lang.reflect.*; 

public class ClassLister { 
  private String currentClassName = ""; 
  private Class currentClass = null; 
  private Vector knownPackages = null; 

  public ClassLister(){ 
    currentClassName = ""; 
    knownPackages = new Vector(); 
    knownPackages.addElement("java.lang."); 
  } 

  public ClassLister(String aClassName) { 
    currentClassName = aClassName; 
    knownPackages = new Vector(); 
    knownPackages.addElement("java.lang."); 
  } 

  public ClassLister(String aClassName, Vector aPackageList) { 
    currentClassName = aClassName; 
    if (knownPackages == null){ 
    knownPackages = aPackageList; 
    } 
    else{ 
      Enumeration enum = aPackageList.elements(); 
      while (enum.hasMoreElements()){ 
        String aPackage = (String)enum.nextElement(); 
        knownPackages.addElement(aPackage); 
      } 
    } 
  } 

  public void setClassName(String aClassName){ 
    this.currentClassName = aClassName; 
  } 

  public String getClassName(){ 
    return this.currentClassName; 
  } 

  public boolean isNameAClass(String aClassName){ 
    Enumeration packages = knownPackages.elements(); 
    Class aClass = null; 
    String fullClassName = ""; 
    boolean result = false; 
    while (packages.hasMoreElements()){ 
      try{ 
        fullClassName = (String)packages.nextElement() + aClassName; 
        aClass = Class.forName(fullClassName); 
        result = true;
//if we get here then the class was successfully found - find first matching class name 
        break; 
      } 
      catch (Exception ex){ 
          //ex.printStackTrace(); 
        System.out.println("no class"); 
        result = false; 
      } 
    } 
    return result; 
  } 

  public void addPackage(String aPackage){ 
    String s = aPackage.trim(); 
    if (s.charAt(s.length() - 1) == '*'){ 
      aPackage = s.substring(0, s.length() - 1); 
      s = aPackage; 
      System.out.println(s); 
    } 
    if (this.knownPackages.contains(s)){return;} 
    this.knownPackages.addElement(s); 
  } 

  public String listMethodArgs(String aMethod) throws ClassNotFoundException{ 
    String result = ""; 
    currentClass = null; 
    try{ 
      currentClass = Class.forName(currentClassName); 

    } 
    catch (ClassNotFoundException noClassEx){ 
      boolean notFound = true; 
      if (knownPackages == null){ 
        throw noClassEx; 
      } 
      Enumeration packages = knownPackages.elements(); 

      String fullClassName = ""; 
      while (packages.hasMoreElements()){ 
        try{ 
          fullClassName = (String)packages.nextElement() + currentClassName; 
          currentClass = Class.forName(fullClassName); 
          break;
//if we get here then the class was successfully found - find first matching class name 
        } 
        catch (ClassNotFoundException ex){ 
          //ex.printStackTrace(); 
          System.out.println("no class"); 
        } 
      } 
      //noClassEx.printStackTrace(); 
    } 
    catch (Exception ex){ 
      //ex.printStackTrace(); 
      System.out.println("Whoops"); 
    } 

    if (currentClass == null) { 
      throw new ClassNotFoundException(); 
    } 
    Method foundMethod = null; 
    Method[] methods = currentClass.getDeclaredMethods(); 
    for (int i=0;i<methods.length;i++){ 
      Method m = methods[i]; 
      if (m.getName().equalsIgnoreCase(aMethod)){ 
        foundMethod = m; 
        break; 
      } 
    } 
    if (foundMethod != null){ 
      Class[] args = foundMethod.getParameterTypes(); 
      for (int i=0;i<args.length;i++){ 
        Class arg = args[i]; 
        result += arg.getName() + " argument" + String.valueOf(i)+ " "; 
        /*e = new ClassElement("Method    " + aMethod.getName() + " : " + 
                         aMethod.getReturnType().getName(), 
                           aMethod.getName()); 
        results.addElement(e);*/ 
      } 
    } 
    return result; 
  } 
  public Vector listMethods() throws ClassNotFoundException{ 
    Vector results = new Vector(); 
    currentClass = null; 
    try{ 
      currentClass = Class.forName(currentClassName); 

    } 
    catch (ClassNotFoundException noClassEx){ 
      boolean notFound = true; 
      if (knownPackages == null){ 
        throw noClassEx; 
      } 
      Enumeration packages = knownPackages.elements(); 

      String fullClassName = ""; 
      while (packages.hasMoreElements()){ 
        try{ 
          fullClassName = (String)packages.nextElement() + currentClassName; 
          currentClass = Class.forName(fullClassName); 
          break;
//if we get here then the class was successfully found - find first matching class name 
        } 
        catch (ClassNotFoundException ex){ 
          //ex.printStackTrace(); 
          System.out.println("no class"); 
        } 
      } 
      //noClassEx.printStackTrace(); 
    } 
    catch (Exception ex){ 
      //ex.printStackTrace(); 
      System.out.println("Whoops"); 
    } 

    if (currentClass == null) { 
      throw new ClassNotFoundException(); 
    } 

    Method[] methodList = currentClass.getDeclaredMethods(); 
    ClassElement e = null; 
    for (int i =0; i < methodList.length; i++){ 
      Method aMethod = methodList[i]; 
      e = new ClassElement("Method    " + aMethod.getName() + " : " + 
                         aMethod.getReturnType().getName(), 
                           aMethod.getName()); 
      results.addElement(e); 
    } 

    return results; 
  } 

  public Vector listAll() throws ClassNotFoundException{ 
    Vector results = new Vector(); 
    currentClass = null; 
    try{ 
      currentClass = Class.forName(currentClassName); 

    } 
    catch (ClassNotFoundException noClassEx){ 
      boolean notFound = true; 
      if (knownPackages == null){ 
        throw noClassEx; 
      } 
      Enumeration packages = knownPackages.elements(); 

      String fullClassName = ""; 
      while (packages.hasMoreElements()){ 
        try{ 
          fullClassName = (String)packages.nextElement() + currentClassName; 
          currentClass = Class.forName(fullClassName); 
          break;
//if we get here then the class was successfully found - find first matching class name 
        } 
        catch (ClassNotFoundException ex){ 
          //ex.printStackTrace(); 
          System.out.println("no class"); 
        } 
      } 
      //noClassEx.printStackTrace(); 
    } 
    catch (Exception ex){ 
      //ex.printStackTrace(); 
      System.out.println("Whoops"); 
    } 

    if (currentClass == null) { 
      throw new ClassNotFoundException(); 
    } 

    Method[] methodList = currentClass.getDeclaredMethods(); 
    ClassElement e = null; 
    for (int i =0; i < methodList.length; i++){ 
      Method aMethod = methodList[i]; 
      e = new ClassElement("Method    " + aMethod.getName() + " : " + 
                         aMethod.getReturnType().getName(), 
                           aMethod.getName()); 
      results.addElement(e); 
    } 

    Field[] fieldList = currentClass.getDeclaredFields(); 
    for (int i =0; i < fieldList.length; i++){ 
      Field aField = fieldList[i]; 
      e = new ClassElement("Member    " + aField.getName() + " : " + 
                         aField.getClass().getName(), 
                           aField.getName()); 
      results.addElement(e); 
    } 

    return results; 
  } 
} 

Listing 7 

package CodeEditor; 
import java.util.*; 

public class CodeClass { 
  public Vector attributes = new Vector(); //list of CodeAttribute 
  public Vector methods = new Vector();    //list of CodeMethod 
  public Vector constructors = new Vector(); //list of CodeConstructor 
  public String className = ""; 
  public String superClass = ""; 
  public Vector interfaces = new Vector();  //list of strings 
  public String scope = "public"; 

  public CodeClass() { 

  } 

} 

Listing 8:
 
package CodeEditor; 

import com.sun.java.swing.*; 
import com.sun.java.swing.text.*; 
import java.util.*; 
import java.awt.*; 
import java.awt.event.*; 

public class CodeDocument extends DefaultStyledDocument implements ActionListener{ 
  ////////////////////////////////////// 
  //these are for the States 
  /////////////////////////////////////// 
  private static final int STATE_TEXT_INPUT = 10; 
  private static final int STATE_CLASS_INPUT = 11; 
  private static final int STATE_VARIABLE_INPUT = 12; 
  private static final int STATE_PACKAGE_INPUT = 13; 
  private static final int STATE_IMPORT_INPUT = 14; 
  private static final int STATE_VARIABLE_TYPE_INPUT = 15; 

  private static final boolean DEBUG = true; //turns off the diagnostic System.out statements 

  //class reflection stuff 
  private ClassLister classLister = new ClassLister(); 
  private Hashtable codeElements = new Hashtable(); 
  private String currentClassName = ""; 
  private String currentTypeName = ""; 
  private Class currentClass = null; 
  private int currentState = STATE_TEXT_INPUT; 
  private CodePackage thePackage = new CodePackage(); 
  private Vector methodListeners = new Vector(); 
  private String currentMethod = ""; 
  private String currentKeyWord = ""; 
  private String oldKeyWord = ""; 
  private int listOffs = 0; 
  private boolean codeReflectionOn = true; 
  //syntax stuff here 
  private String word = ""; 
  private SimpleAttributeSet bold = new SimpleAttributeSet(); 
  private SimpleAttributeSet string = new SimpleAttributeSet(); 
  private SimpleAttributeSet normal = new SimpleAttributeSet(); 
  private SimpleAttributeSet number = new SimpleAttributeSet(); 
  private SimpleAttributeSet comments = new SimpleAttributeSet(); 

  private int currentPos = 0; 
  private Vector keywords = new Vector(); 
  public static int STRING_MODE = 10; 
  public static int TEXT_MODE = 11; 
  public static int NUMBER_MODE = 12; 
  public static int COMMENT_MODE = 13; 
  private int mode = TEXT_MODE; 

  public CodeDocument() { 
   //set the bold attribute 
   StyleConstants.setBold(bold, true); 
   StyleConstants.setForeground(string, Color.red); 
   StyleConstants.setForeground(number, Color.magenta); 
   StyleConstants.setForeground(comments, Color.blue); 
   StyleConstants.setItalic(comments, true); 
  } 

  //reflection methods 
  /** 
  */ 
  private void checkState(){ 
    switch (this.currentState){ 
      case (this.STATE_CLASS_INPUT):{ 
        this.thePackage.outerClass.className = word; 
        if (DEBUG) { 
          System.out.println("Class is " + thePackage.outerClass.className); 
        } 
      } 
      break; 
      case (this.STATE_IMPORT_INPUT):{ 
        if (DEBUG) { 
          System.out.println(word); 
        } 
        this.thePackage.imports.addElement(word); 
        classLister.addPackage(word); 
      } 
      break; 
      case (this.STATE_PACKAGE_INPUT):{ 
        if (DEBUG) { 
          System.out.println(word); 
        } 
        this.thePackage.packageName = word; 
      } 
      break; 
      case (this.STATE_TEXT_INPUT):{ 
        if (DEBUG) { 
          System.out.println(word); 
        } 
      } 
      break; 
      case (this.STATE_VARIABLE_INPUT):{ 
        if (DEBUG) { 
          System.out.println("Variable: " + word); 
          System.out.println("Variable Type: " + currentTypeName); 
        } 
      } 
      break; 
      case (this.STATE_VARIABLE_TYPE_INPUT):{ 
        if (DEBUG) { 
          System.out.println("Current variable type: " + word); 
        } 
        currentTypeName = word; 
      } 
      break; 
    }//end of switch 
  } 

  /** 
  This method checks for a possible state change 
  */ 
  private void changeState(){ 
    String s = word.trim(); 
    if (s.equalsIgnoreCase("package")){ 
    //package state 
      this.currentState = this.STATE_PACKAGE_INPUT; 
    } 
    else if (s.equalsIgnoreCase("import")){ 
      this.currentState = this.STATE_IMPORT_INPUT; 
    } 
    else if (s.equalsIgnoreCase("class")){ 
      this.currentState = this.STATE_CLASS_INPUT; 
      this.thePackage.outerClass.scope = this.oldKeyWord; 
    } 
    else if (this.currentState != this.STATE_VARIABLE_TYPE_INPUT){ 
      String tmp = word.trim(); 
      if (tmp == ""){ 
        return; 
      } 
      if (classLister.isNameAClass(word)){ 
        this.currentState = this.STATE_VARIABLE_INPUT; 
        this.currentTypeName = word; 
      } 
      else{ 
        this.currentTypeName = ""; 
      } 
      if (DEBUG) { 
        System.out.println("Current variable type: " + currentTypeName); 
      } 
    } 
    else if ((this.currentState == this.STATE_VARIABLE_TYPE_INPUT) && 
             (this.currentTypeName != "")){ 
      this.currentState = this.STATE_VARIABLE_INPUT; 
    } 

    if (this.DEBUG){ 
      stateOut(); 
    } 
  } 

  /** 
  */ 
  private void handleDot(){ 
    SimpleAttributeSet inputAttributes = new SimpleAttributeSet(); 
    classLister.setClassName(this.currentTypeName); 
    try{ 
      Vector listing = classLister.listAll(); 
      JComboBox c = new JComboBox(listing); 
      c.addActionListener(this); 

      StyleConstants.setComponent(inputAttributes, c); 

      super.insertString(currentPos + 1, " ", inputAttributes); 
    } 
    catch (Exception ex){ 
      ex.printStackTrace(); 
    } 
  } 

  /** 
  */ 
  public void handleOpenParen(){ 
    classLister.setClassName(this.currentTypeName); 
    try{ 
      String args = classLister.listMethodArgs(currentMethod); 
      ActionEvent ev = new ActionEvent(this, 0, args); 
      this.fireMethodEvent(ev); 
    } 
    catch (Exception ex){ 
      ex.printStackTrace(); 
    } 
  } 

  /** 
  */ 
  private void checkForStateChange(char chr){ 
    switch (chr){ 
      case ' ': case '\n':{ 
         checkState(); 
         changeState(); 
      } 
      break; 
      case ('.'):{ 
        int oldOffs = currentPos; 
        if ((this.currentState == this.STATE_VARIABLE_INPUT) | 
            (this.currentState == this.STATE_VARIABLE_TYPE_INPUT)){ 
          checkState(); 
          handleDot(); 
        } 
        listOffs = oldOffs + 1; 
        if (this.DEBUG){ 
          stateOut(); 
        } 
      } 
      break; 
      case ('('):{ 
        int oldOffs = currentPos; 
        if ((this.currentState == this.STATE_VARIABLE_INPUT) | 
            (this.currentState == this.STATE_VARIABLE_TYPE_INPUT)){ 
          checkState(); 
          handleOpenParen(); 
        } 
        listOffs = oldOffs + 1; 
        if (this.DEBUG){ 
          stateOut(); 
        } 
      } 
      case (';'):case ('{'):{ 
        oldKeyWord = currentKeyWord; 
        checkState(); 
        this.currentState = this.STATE_TEXT_INPUT; 
        if (this.DEBUG){ 
          stateOut(); 
        } 
      } 
    }// end switch 
  } 

  /** 
  */ 
  private void stateOut(){ 
    String s = ""; 
     switch (this.currentState){ 
       case (this.STATE_CLASS_INPUT):{ 
         s = "STATE_CLASS_INPUT"; 
       } 
       break; 
       case (this.STATE_IMPORT_INPUT):{ 
         s = "STATE_IMPORT_INPUT"; 
       } 
       break; 
       case (this.STATE_PACKAGE_INPUT):{ 
         s = "STATE_PACKAGE_INPUT"; 
       } 
       break; 
       case (this.STATE_TEXT_INPUT):{ 
         s = "STATE_TEXT_INPUT"; 
       } 
       break; 
       case (this.STATE_VARIABLE_INPUT):{ 
         s = "STATE_VARIABLE_INPUT"; 
       } 
       break; 
       case (this.STATE_VARIABLE_TYPE_INPUT):{ 
         s = "STATE_VARIABLE_TYPE_INPUT"; 
       } 
       break; 
     } 
    System.out.println(s); 
  } 

  ////////////////////////////////////////////////////////////////////////////// 
  //events 
  ////////////////////////////////////////////////////////////////////////////// 
  /** 
  */ 
  public void actionPerformed(ActionEvent e) { 
    //TODO: implement this java.awt.event.ActionListener method; 

    try{ 
      JComboBox comp = (JComboBox)e.getSource(); 
      ClassElement elem = (ClassElement) comp.getSelectedItem(); 
      String item = elem.getElementValue(); 
      this.remove(listOffs, 1); 
      super.insertString(listOffs, item, null); 
      currentMethod = item; 
    } 
    catch (Exception ex){ 
      ex.printStackTrace(); 
    } 
  } 

  ////////////////////////////////////////////////////////////////////////////// 
  //Event notification 
  ////////////////////////////////////////////////////////////////////////////// 
  /** 
  */ 
  public void fireMethodEvent(ActionEvent ev){ 
    Enumeration e = methodListeners.elements(); 
    while(e.hasMoreElements()){ 
      MethodListener listener = (MethodListener)e.nextElement(); 
      listener.methodAction(ev); 
    } 
  } 

  ////////////////////////////////////////////////////////////////////////////// 
  //Event registration 
  ////////////////////////////////////////////////////////////////////////////// 
  /** 
  */ 
  public void addMethodListener(MethodListener listener){ 
    methodListeners.addElement(listener); 
  } 

  //////////////////////////////////////////////////////////////////////////// 
  //syntax methods 
  //////////////////////////////////////////////////////////////////////////// 
  private void insertKeyword(String str, int pos){ 
    try{ 
      //remove the old word and formatting 
      this.remove(pos - str.length(), str.length()); 
      /*replace it with the same word, but new formatting 
      *we MUST call the super class insertString method here, otherwise we 
      *would end up in an infinite loop !!!!!*/ 
      super.insertString(pos - str.length(), str, bold); 
    } 
    catch (Exception ex){ 
      ex.printStackTrace(); 
    } 
  } 

  private void insertTextString(String str, int pos){ 
    try{ 
      //remove the old word and formatting 
      this.remove(pos,str.length()); 
      super.insertString(pos, str, string); 
    } 
    catch (Exception ex){ 
      ex.printStackTrace(); 
    } 
  } 

  private void insertNumberString(String str, int pos){ 
    try{ 
      //remove the old word and formatting 
      this.remove(pos,str.length()); 
      super.insertString(pos, str, number); 
    } 
    catch (Exception ex){ 
      ex.printStackTrace(); 
    } 
  } 

  private void insertCommentString(String str, int pos){ 
    try{ 
      //remove the old word and formatting 
      this.remove(pos,str.length()); 
      super.insertString(pos, str, comments); 
    } 
    catch (Exception ex){ 
      ex.printStackTrace(); 
    } 
  } 

  private void checkForString(){ 
    int offs = this.currentPos; 
    Element element = this.getParagraphElement(offs); 
    String elementText = ""; 
    try{ 
      //this gets our chuck of current text for the element we're on 
      elementText = this.getText(element.getStartOffset(), 
                                 element.getEndOffset() - element.getStartOffset()); 
    } 
    catch(Exception ex){ 
      //whoops! 
      System.out.println("no text"); 
    } 
    int strLen = elementText.length(); 
    if (strLen == 0) {return;} 
    int i = 0; 

    if (element.getStartOffset() > 0){ 
      //translates backward if neccessary 
      offs = offs - element.getStartOffset(); 
    } 
    int quoteCount = 0; 
    if ((offs >= 0) && (offs <= strLen-1)){ 
      i = offs; 
      while (i >0){ 
      //the while loop walks back until we hit a delimiter 

        char charAt = elementText.charAt(i); 
        if ((charAt == '"')){ 
         quoteCount ++; 
        } 
        i--; 
      } 
      int rem = quoteCount % 2; 
      //System.out.println(rem); 
      mode = (rem == 0) ? TEXT_MODE: STRING_MODE; 
    } 
  } 

  private void checkForKeyword(){ 
    if (mode != TEXT_MODE) { 
      return; 
    } 
    int offs = this.currentPos; 
    Element element = this.getParagraphElement(offs); 
    String elementText = ""; 
    try{ 
      //this gets our chuck of current text for the element we're on 
      elementText = this.getText(element.getStartOffset(),
	  element.getEndOffset() - element.getStartOffset()); 
    } 
    catch(Exception ex){ 
      //whoops! 
      System.out.println("no text"); 
    } 
    int strLen = elementText.length(); 
    if (strLen == 0) {return;} 
    int i = 0; 

    if (element.getStartOffset() > 0){ 
      //translates backward if neccessary 
      offs = offs - element.getStartOffset(); 
    } 
    if ((offs >= 0) && (offs <= strLen-1)){ 
      i = offs; 
      while (i >0){ 
      //the while loop walks back until we hit a delimiter 
        i--; 
        char charAt = elementText.charAt(i); 
        if ((charAt == ' ') | (i == 0) | (charAt =='(') | (charAt ==')') | 
            (charAt == '{') | (charAt == '}')){ //if i == 0 then we're at the begininng 
          if(i != 0){ 
            i++; 
          } 
          word = elementText.substring(i, offs);//skip the period 

          String s = word.trim().toLowerCase(); 
          //this is what actually checks for a matching keyword 
		            if (keywords.contains(s)){ 
            insertKeyword(word, currentPos); 
          } 
          break; 
        } 
      } 
    } 
  } 

  private void checkForNumber(){ 
    int offs = this.currentPos; 
    Element element = this.getParagraphElement(offs); 
    String elementText = ""; 
    try{ 
      //this gets our chuck of current text for the element we're on 
      elementText = this.getText(element.getStartOffset(), 
                                 element.getEndOffset() - element.getStartOffset()); 
    } 
    catch(Exception ex){ 
      //whoops! 
      System.out.println("no text"); 
    } 
    int strLen = elementText.length(); 
    if (strLen == 0) {return;} 
    int i = 0; 

    if (element.getStartOffset() > 0){ 
      //translates backward if neccessary 
      offs = offs - element.getStartOffset(); 
    } 
    mode = TEXT_MODE; 
    if ((offs >= 0) && (offs <= strLen-1)){ 
      i = offs; 
      while (i >0){ 
      //the while loop walks back until we hit a delimiter 
        char charAt = elementText.charAt(i); 
        if ((charAt == ' ') | (i == 0) | (charAt =='(') | (charAt ==')') | 
            (charAt == '{') | (charAt == '}')){ //if i == 0 then we're at the begininng 
          if(i != 0){ 
            i++; 
          } 
          mode = NUMBER_MODE; 
          break; 
        } 
        else if (!(charAt >= '0' & charAt <= '9' | charAt=='.' 
                  | charAt=='+' | charAt=='-' 
                  | charAt=='/' | charAt=='*'| charAt=='%' | charAt=='=')){ 
          mode = TEXT_MODE; 
          break; 
        } 
        i--; 
      } 
    } 
  } 

  private void checkForComment(){ 
    int offs = this.currentPos; 
    Element element = this.getParagraphElement(offs); 
    String elementText = ""; 
    try{ 
      //this gets our chuck of current text for the element we're on 
      elementText = this.getText(element.getStartOffset(),
	  element.getEndOffset() - element.getStartOffset()); 
    } 
    catch(Exception ex){ 
      //whoops! 
      System.out.println("no text"); 
    } 
    int strLen = elementText.length(); 
    if (strLen == 0) {return;} 
    int i = 0; 

    if (element.getStartOffset() > 0){ 
      //translates backward if neccessary 
      offs = offs - element.getStartOffset(); 
    } 
    if ((offs >= 1) && (offs <= strLen-1)){ 
      i = offs; 
      char commentStartChar1 = elementText.charAt(i-1); 
      char commentStartChar2 = elementText.charAt(i); 
      if (commentStartChar1 == '/' && commentStartChar2 == '*'){ 
          mode = COMMENT_MODE; 
          this.insertCommentString("/*", currentPos-1); 
      } 
      else if (commentStartChar1 == '*' && commentStartChar2 == '/'){ 
          mode = TEXT_MODE; 
          this.insertCommentString("*/", currentPos-1); 
      } 
    } 
  } 

  private void processChar(String str){ 
    char strChar = str.charAt(0); 
    if (mode != this.COMMENT_MODE){ 
      mode = TEXT_MODE; 
    } 
      switch (strChar){ 
        case ('{'):case ('}'):case (' '): case('\n'): 
        case ('('):case (')'):case (';'):case ('.'):{ 
          checkForKeyword(); 
          if (mode == STRING_MODE && strChar == '\n'){ 
            mode = TEXT_MODE; 
          } 
          if (codeReflectionOn){ 
            checkForStateChange(strChar); 
          } 
        } 
        break; 
        case ('"'):{ 
          insertTextString(str, currentPos); 
          this.checkForString(); 
        } 
        break; 
        case ('0'):case ('1'):case ('2'):case ('3'):case ('4'): 
        case ('5'):case ('6'):case ('7'):case ('8'):case ('9'):{ 
          checkForNumber(); 
        } 
        break; 
        case ('*'):case ('/'):{ 
          checkForComment(); 
        } 
        break; 
      } 
      if (mode == this.TEXT_MODE){ 
        this.checkForString(); 
      } 
      if (mode == this.STRING_MODE){ 
        insertTextString(str, this.currentPos); 
      } 
      else if (mode == this.NUMBER_MODE){ 
        insertNumberString(str, this.currentPos); 
      } 
      else if (mode == this.COMMENT_MODE){ 
        insertCommentString(str, this.currentPos); 
      } 

  } 

  private void processChar(char strChar){ 
      char[] chrstr = new char[1]; 
      chrstr[0] = strChar; 
      String str = new String(chrstr); 
      processChar(str); 
  } 

  public void insertString(int offs, 
                          String str, 
                          AttributeSet a) throws BadLocationException{ 
    super.insertString(offs, str, normal); 

    int strLen = str.length(); 
    int endpos = offs + strLen; 
    int strpos; 
    codeReflectionOn = strLen == 1; 
    for (int i=offs;i<endpos;i++){ 
      currentPos = i; 
      strpos = i - offs; 
      processChar(str.charAt(strpos)); 
    } 
    currentPos = offs; 
  } 

  public Vector getKeywords(){ 
    return this.keywords; 
  } 

  public void setKeywords(Vector aKeywordList){ 
    if (aKeywordList != null){ 
      this.keywords = aKeywordList; 
    } 
  } 
} 

Listing 9: 
  

package CodeEditor; 
import java.util.*; 

public class CodePackage { 
  public String packageName = ""; 
  public Vector imports = new Vector(); 
  public CodeClass outerClass = new CodeClass(); 
  public Vector innerClasses = new Vector(); 
  public CodePackage() { 
  } 
} 

Listing 10:
 
package CodeEditor; 
import java.awt.event.*; 

public interface MethodListener { 
  public void methodAction(ActionEvent e); 

} 
  
  
      
 

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