Java LinkedList's Listiterator

Java LinkedList's Listiterator

@author Ixenos

Listiterator<e> is an interface that inherits from Iterator<e>

Therefore, Listiterator Note:

1. iterators do not store references to all elements, only two pointers, one pointer to the last returned element, and another element that is not in the next step;

2. Synchronize the internal and external modcount before the iteration begins, check for synchronization during the iteration, and if the external structure changes, the iteration fails quickly (fast-fails mechanism);

　　3.ListIterator can be counted as half a linkedlist view because the external structure (add, remove) can be modified on the way to the iteration.

Listiterator (int index) source analysis

Listiterator

Listiterator (int index)

Returns a list iterator (in the appropriate order) for the elements in this list, starting at the specified position in the list .

Parameters:

index-The index of the first element to be returned from the list iterator (by calling the next method)

Return:

The Listiterator (in the appropriate order) of the elements in this list, starting at the specified position in the list

Thrown:

IndexOutOfBoundsException-If the index is out of range (index < 0 | | index > Size ())

Pass:

　　　Internal classes Private class Listitr implements listiterator<e> implementation

1 //iterators do not store numeric values! is to return one time per iteration2 //a powerful Listiterator method in LinkedList3 4    PublicListiterator<e> Listiterator (intindex) {5 Checkpositionindex (index);6         return NewLISTITR (index);//calling an anonymous object of the inner class Listitr7     }8 9 //the Listiterator interface is given to the internal class implementation for compatibility with the iterator interface because the Listiterator interface inherits from the iterator interfaceTen     Private classListitrImplementslistiterator<e> {//implements the Listiterator interface One         PrivateNode<e> lastreturned;//points to the last returned element A         PrivateNode<e> Next;//point to the next non-involved element -         Private intNextindex; -         Private intExpectedmodcount =Modcount; the  -Listitr (intindex) { -             //assert Ispositionindex (index); -Next = (index = = size)?NULL: node (index); +Nextindex =index; -         } +  A          Public BooleanHasnext () { at             returnNextindex <size; -         } -  -          PublicE Next () { - checkforcomodification (); -             if(!Hasnext ()) in                 Throw Newnosuchelementexception (); -  tolastreturned =Next; +Next =Next.next; -nextindex++; the             returnLastreturned.item; *         } $ Panax Notoginseng          Public Booleanhasprevious () { -             returnNextindex > 0; the         } +  A          PublicE Previous () { the checkforcomodification (); +             if(!hasprevious ()) -                 Throw Newnosuchelementexception (); $  $lastreturned = Next = (Next = =NULL) ?Last:next.prev; -nextindex--; -             returnLastreturned.item; the         } - Wuyi          Public intNextindex () { the             returnNextindex; -         } Wu  -          Public intPreviousindex () { About             returnNextIndex-1;  $         } -      - //can delete yo -          Public voidRemove () { ACheckforcomodification ();//Make sure the external modcount is not changed . +             if(lastreturned = =NULL) the                 Throw Newillegalstateexception (); -  $Node<e> Lastnext =Lastreturned.next; the unlink (lastreturned); the             if(Next = =lastreturned) theNext =Lastnext; the             Else -nextindex--; inlastreturned =NULL; theexpectedmodcount++;//Remove external elements modcount++ so the internal expectedmodcount is also + + to synchronize the         } About  the          Public voidset (e e) { the             if(lastreturned = =NULL)//Make sure the external modcount is not changed . the                 Throw Newillegalstateexception (); + checkforcomodification (); -Lastreturned.item =e; the         }Bayi  the          Public voidAdd (e e) { the checkforcomodification (); -lastreturned =NULL; -             if(Next = =NULL) theLinklast (e);//If the next pointer is at the end of the team, add it directly to the tail . the             Else theLinkbefore (E, next);//Otherwise, insert the next pointer to the front of the element thenextindex++; -expectedmodcount++;//Remove external elements modcount++ so the internal expectedmodcount is also + + to synchronize the  the         } the 94          Public voidForeachremaining (consumer<?SuperE>action) { theObjects.requirenonnull (action);//throws a null pointer exception if action is empty the              while(Modcount = = Expectedmodcount && Nextindex <size) { the action.accept (next.item);98lastreturned =Next; AboutNext =Next.next; -nextindex++;101             }102 checkforcomodification ();103         } 104  the //An external structure modification is an iterative fast failure fast-fails106         Final voidcheckforcomodification () {107             if(Modcount! =expectedmodcount)108                 Throw Newconcurrentmodificationexception ();109         } the}

Listiterator Source

Descending iterations with LISTITR implementation

Descendingiterator

Descendingiterator ()

returns an iterator that iterates over the elements of this double-ended queue in reverse order. Elements are returned in the order from the last (tail) to the first (head).

The essence is to modify the pointer in the key operation

Return:

An iterator that iterates over the elements of this double-ended queue in reverse order

Start from the following versions:

1.6

1   /**Descending Iteration2      * @since1.63      */4 //sort is the order ascending means that the ascending descending represents the descending5      PublicIterator<e>Descendingiterator () {6         return Newdescendingiterator ();7     }8 9     /**Ten * Adapter to provide descending iterators via listitr.previous One      */ A //using Lisitr to implement descending iterations -     Private classDescendingiteratorImplementsIterator<e> { -         Private FinalListitr ITR =Newlistitr (Size ());  the          Public BooleanHasnext () { -             returnItr.hasprevious ();//using the original method, we changed the return -         } -          PublicE Next () { +             returnItr.previous ();//using the original method, we changed the return -         } +          Public voidRemove () { A Itr.remove (); at         } -}

Descendingiterator Source

Java LinkedList's Listiterator