Iterator Interface Diagram

Iterator Interface Specification

Invariant

An Iterator object...

- is used to treat a collection (theCollection) like a linear list of items.

- position maintains a desginated position within theCollection

- 0 <= position <= theCollection.size()

(position == 0 denotes the front of the list and position == size() at the rear)

Update Method

public void remove ()

pre: isRemovable

post(expected):

theCollection == theCollection@pre with the position^th@pre item removed (i.e., the item most recently returned by next() is the one removed)

and theCollection.size() == theCollection.size()@pre - 1

and position == position@pre - 1

(i.e., the iterator is effectively unchanged in position)

and isRemovable == false

note: This method must be supplied by the implementing class.

Query Methods

public boolean hasNext( )

post: result == ( position != theCollection.size() )

(i.e. result is false exactly when iterator is positioned at the rear of

theCollection)

note: This method must be supplied by the implementing class.

public ItemType next ()

pre: hasNext()

post: position == position@pre + 1

(i.e. the iterator's position advances by one item)

and result == the position^th item

and isRemovable == true

note: This method must be supplied by the implementing class.