Collections, Maps and Iterators - Java - page 850

Display 16.4 Selected Methods in the List<T> Interface (part 3 of 3)
public int lastIndexOf(Object target)
Returns the index of the last element that is equal to target . Uses the method equals of the
object target to test for equality. Returns 1 if target is not found.
public List<T> subList(int fromIndex, int toIndex)
Returns a view of the elements at locations fromIndex to toIndex of the calling object; the
object at fromIndex is included; the object, if any, at toIndex is not included. The view uses ref-
erences into the calling object; so, changing the view can change the calling object. The returned
object will be of type List<T> but need not be of the same type as the calling object. Returns an
empty List<T> if fromIndex equals toIndex .
ListIterator<T> listIterator( )
Returns a list iterator for the calling object. (Iterators are discussed in Section 16.3.)
ListIterator<T> listIterator(int index)
Returns a list iterator for the calling object starting at index . The first element to be returned by
the iterator is the one at index . (Iterators are discussed in Section 16.3.)
Collection Interfaces
The primary interfaces for collection classes are the Collection<T> , Set<T> , and List<T>
interfaces. Both the Set<T> and the List<T> interfaces are derived from the Collection<T>
interface. The Set<T> interface is for collections that do not allow repetition of elements and
do not impose an order on their elements. The List<T> interface is for collections that do allow
repetition of elements and do impose an order on their elements.
For-Each Loops
You can use a for-each loop with any of the collections discussed in this chapter.
PITFALL: Optional Operations
What is the point of an optional method heading in an interface? The whole point of
an interface is to specify what methods can be used with an object of the interface type
so that you can write code for an arbitrary object of the interface type. The reasoning
behind these optional methods is that they normally would be implemented, but in
unusual situations a programmer may leave them “unsupported.” (The alternative
would be to have two interfaces, one with and one without the optional operations.
Uncharacteristically, Java designers opted for a smaller number of interfaces.) But there
is still more to the story.