Collections and Concurrency - JavaFX 8: A Definitive Guide to Building Desktop, Mobile, and Embedded Java Clients - page 274

boolean wasAdded() •

boolean wasRemoved() •

boolean wasReplaced()

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boolean wasPermutated() •

int getFrom() •

int getTo() •

int getAddedSize() •

List<E> getAddedSublist()

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int getRemovedSize() •

List<E> getRemoved() •

int getPermutation(int i) •

ObservableList<E> getList()
The next() and reset() methods control a cursor that iterates through all the discrete changes in the event
object. On entry to the onChange() method of ListChangeListener , the cursor is positioned before the first discrete
change. You must call the next() method to move the cursor to the first discrete change. Succeeding calls to the
next() method will move the cursor to the remaining discrete changes. If the next discrete change is reached, the
return value will be true . If the cursor is already on the last discrete change, the return value will be false . Once
the cursor is positioned on a valid discrete change, the methods wasAdded() , wasRemoved() , wasReplaced() , and
wasPermutated() can be called to determine the kind of change the discrete change represents.

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■ the wasAdded() , wasRemoved() , wasReplaced() , and wasPermutated() methods are not orthogonal.
a discrete change is a replacement only if it is both an addition and a removal. the proper order for testing the kind of
a discrete change, therefore, is to first determine whether it is a permutation or a replacement and then to determine
whether it is an addition or a removal.

Caution

Once you have determined the kind of discrete change, you can call the other methods to get more information
about it. For addition, the getFrom() method returns the index in the observable list where new elements were
added; the getTo() method returns the index of the element that is one past the end of the added elements; the
getAddedSize() method returns the number of elements that were added; and the getAddedSublist() method
returns a List<E> that contains the added elements. For removal, the getFrom() and getTo() methods both return
the index in the observable list where elements were removed; the getRemovedSize() method returns the number of
elements that were removed; and the getRemoved() method returns a List<E> that contains the removed elements.
For replacement, both the methods that are relevant for addition and the methods that are relevant for removal
should be examined, because a replacement can be seen as a removal followed by an addition at the same index.
For permutation, the getPermutation(int i) method returns the index of an element in the observable list after the
permutation whose index in the observable list before the permutation was i . In all situations, the getList() method
always returns the underlying observable list.
In the example shown in Listing 7-2, we perform various list manipulations after attaching a ListChangeListener
to an ObservableList . The implementation of ListChangeListener , called MyListener , includes a pretty printer for
the ListChangeListener.Change object, and prints out the list change event object when an event is fired.