Basic Text Components - The Definitive Guide to Java Swing - page 538

The getChange() method of DocumentEvent requires an Element to return a
DocumentEvent.ElementChange . You normally use the default root element from the
Document , as in the following example.
Document documentSource = documentEvent.getDocument();
Element rootElement = documentSource.getDefaultRootElement();
DocumentEvent.ElementChange change = documentEvent.getChange(rootElement);
Once you have your DocumentEvent.ElementChange instance, you can find out the added
and removed elements, if you need that level of information.
public interface DocumentEvent.ElementChange {
public Element[ ] getChildrenAdded();
public Element[ ] getChildrenRemoved();
public Element getElement();
public int getIndex();
}
Caret and Highlighter Interfaces
Now that you understand the data model aspect of a text component, you can look at some
aspects of its selection rendering through the Caret and Highlighter interfaces. Remember
that these are properties of the text component, not the data model.
The Caret interface describes what's usually referred to as the cursor : the location in the
document where you can insert text. The Highlighter interface provides the basis for how to
paint selected text. These two interfaces, their related interfaces, and their implementations
are rarely altered. The text components simply use their default implementations with the
DefaultCaret and DefaultHighlighter classes.
Although you probably won't alter the caret and highlighter behavior for a text component,
you should know that there are many interrelated classes working together. For the Highlighter
interface, the predefined implementation is called DefaultHighlighter , which extends another
implementation called LayeredHighlighter . The Highlighter also manages a collection of
Highlighter.Highlight objects to designate highlighted sections.
The DefaultHighlighter creates a DefaultHighlighter.HighlightPainter to paint
the highlighted section(s) of text. The HighlightPainter is an implementation of the
Highlighter.HighlightPainter interface and extends the LayeredHighlighter.LayerPainter
class. Each section to paint is described by a Highlighter.Highlight , where the Highlighter
manages the set. The actual HighlightPainter is created by the DefaultCaret implementation.
The Highlighter interface describes how to paint selected text within a text component. If
you don't like the color, you can simply change the TextField.selectionBackground UI property
setting to a different color.
public interface Highlighter {
// Properties
public Highlighter.Highlight[ ] getHighlights();
// Other methods
public Object addHighlight(int p0, int p1, Highlighter.HighlightPainter p)
throws BadLocationException;