ListIterator previous 名不符實

在用ListIterator previous時遇到一個問題，參見下面範例程式碼：

               ListIterator< HistoryItem> iterators = curStack.listIterator();
                while ( iterators.hasNext() ) {
                    HistoryItem item = iterators.next();
                    if ( item.getActivity() == activity ) {

                item = iterators.previous();

                        ......
                        break;
 
                    }
                }

在調用ListIterator::next後，希望調用previous返回上一個item，但是不正確，返回的還是當前的item.

分析下源碼是這樣的：

        public E previous() {
            if (expectedModCount == modCount) {
                try {
                    E result = get(pos);               //  pos是當前位置，返回當前item，並且pos-1
                    lastPosition = pos;
                    pos--;
                    return result;
                } catch (IndexOutOfBoundsException e) {
                    throw new NoSuchElementException();
                }
            }
            throw new ConcurrentModificationException();
        }

        public E next() {
            if (expectedModCount == modCount) {
                try {
                    E result = get(pos + 1);             // 返回當前下一個item，並且pos+1
                    lastPosition = ++pos;
                    return result;
                } catch (IndexOutOfBoundsException e) {
                    throw new NoSuchElementException();
                }
            }
            throw new ConcurrentModificationException();
        }

由此可見，previous只是把索引指向前一個item，返回的仍然是當前的item；而next是真的返回下一個item。