/** * Returns an iterator over the elements in this list in proper sequence. * * <p>The returned iterator is <a href="#fail-fast"><i>fail-fast</i></a>. * * @return an iterator over the elements in this list in proper sequence */ public Iterator<E> iterator(){ returnnew Itr(); }
/** * An optimized version of AbstractList.Itr */ privateclassItrimplementsIterator<E> { int cursor; // index of next element to return int lastRet = -1; // index of last element returned; -1 if no such int expectedModCount = modCount;
publicbooleanhasNext(){ return cursor != size; }
@SuppressWarnings("unchecked") public E next(){ checkForComodification(); int i = cursor; if (i >= size) thrownew NoSuchElementException(); Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) thrownew ConcurrentModificationException(); cursor = i + 1; return (E) elementData[lastRet = i]; }
publicvoidremove(){ if (lastRet < 0) thrownew IllegalStateException(); checkForComodification();
@Override @SuppressWarnings("unchecked") publicvoidforEachRemaining(Consumer<? super E> consumer){ Objects.requireNonNull(consumer); finalint size = ArrayList.this.size; int i = cursor; if (i >= size) { return; } final Object[] elementData = ArrayList.this.elementData; if (i >= elementData.length) { thrownew ConcurrentModificationException(); } while (i != size && modCount == expectedModCount) { consumer.accept((E) elementData[i++]); } // update once at end of iteration to reduce heap write traffic cursor = i; lastRet = i - 1; checkForComodification(); }
finalvoidcheckForComodification(){ if (modCount != expectedModCount) thrownew ConcurrentModificationException(); } }
public E next(){ checkForComodification(); if (!hasNext()) thrownew NoSuchElementException(); lastReturned = next; next = next.next; nextIndex++; return lastReturned.item; }
/** * LinkedList获取指定元素 */ public E get(int index){ checkElementIndex(index); return node(index).item; }
/** * Returns the (non-null) Node at the specified element index. */ Node<E> node(int index){ // assert isElementIndex(index); if (index < (size >> 1)) { Node<E> x = first; for (int i = 0; i < index; i++) x = x.next; return x; } else { Node<E> x = last; for (int i = size - 1; i > index; i--) x = x.prev; return x; } }