AbstractList (Java Platform SE 8 ) (original) (raw)

Returns a view of the portion of this list between the specified

fromIndex

, inclusive, and

toIndex

, exclusive. (If

fromIndex

and

toIndex

are equal, the returned list is empty.) The returned list is backed by this list, so non-structural changes in the returned list are reflected in this list, and vice-versa. The returned list supports all of the optional list operations supported by this list.

This method eliminates the need for explicit range operations (of the sort that commonly exist for arrays). Any operation that expects a list can be used as a range operation by passing a subList view instead of a whole list. For example, the following idiom removes a range of elements from a list:

      list.subList(from, to).clear();
 

Similar idioms may be constructed for

indexOf

and

lastIndexOf

, and all of the algorithms in the

Collections

class can be applied to a subList.

The semantics of the list returned by this method become undefined if the backing list (i.e., this list) is structurally modified in any way other than via the returned list. (Structural modifications are those that change the size of this list, or otherwise perturb it in such a fashion that iterations in progress may yield incorrect results.)

This implementation returns a list that subclassesAbstractList. The subclass stores, in private fields, the offset of the subList within the backing list, the size of the subList (which can change over its lifetime), and the expectedmodCount value of the backing list. There are two variants of the subclass, one of which implements RandomAccess. If this list implements RandomAccess the returned list will be an instance of the subclass that implements RandomAccess.

The subclass's set(int, E), get(int),add(int, E), remove(int), addAll(int, Collection) and removeRange(int, int) methods all delegate to the corresponding methods on the backing abstract list, after bounds-checking the index and adjusting for the offset. TheaddAll(Collection c) method merely returns addAll(size, c).

The listIterator(int) method returns a "wrapper object" over a list iterator on the backing list, which is created with the corresponding method on the backing list. The iterator method merely returns listIterator(), and the size method merely returns the subclass's size field.

All methods first check to see if the actual modCount of the backing list is equal to its expected value, and throw aConcurrentModificationException if it is not.