Interface for document change notifications. This provides detailed information to Document observers about how the Document changed. It provides high level information such as type of change and where it occurred, as well as the more detailed structural changes (What Elements were inserted and removed).
@author
Timothy Prinzing
@version
1.23 12/19/03
See Also
javax.swing.text.Document , DocumentListener
Gets the change information for the given element. The change information describes what elements were added and removed and the location. If there were no changes, null is returned.

This method is for observers to discover the structural changes that were made. This means that only elements that existed prior to the mutation (and still exist after the mutatino) need to have ElementChange records. The changes made available need not be recursive.

For example, if the an element is removed from it's parent, this method should report that the parent changed and provide an ElementChange implementation that describes the change to the parent. If the child element removed had children, these elements do not need to be reported as removed.

If an child element is insert into a parent element, the parent element should report a change. If the child element also had elements inserted into it (grandchildren to the parent) these elements need not report change.

Parameters
elemthe element
Return
the change information, or null if the element was not modified
Gets the document that sourced the change event.
Return
the document
Returns the length of the change.
Return
the length >= 0
Returns the offset within the document of the start of the change.
Return
the offset >= 0
Gets the type of event.
Return
the type