java - 为什么我的reverse()方法会反转两个MyLinkedList对象？

Question

我正在创建一个双向链表类，但我被这个反向()方法困住了。我希望使用reverse()方法创建并返回一个新的MyLinkedList，它与旧的MyLinkedList相反，而不改变旧的。

public MyLinkedList<AnyType> reverse()
{
   MyLinkedList<AnyType> list = this;

   for(int i=0,j=list.theSize-1; i < list.theSize/2; i++, j--)
       list.swap(i,j);

   return list;
}

public void swap(int index1, int index2)
{
        if(index1 == index2)
            return;
        else if(index1 > theSize-1 || index2 > theSize-1)
        {
            try{
                throw new IndexOutOfBoundsException();
            }
            catch(IndexOutOfBoundsException e)
            {
                System.out.println("IndexOutOfBoundsException\n");
                return;
            }             
        }
        Node<AnyType> first;
        Node<AnyType> last;
        if(index1 < index2)
        {
            first = this.getNode(index1);
            last = this.getNode(index2);
        }
        else
        {
            first = this.getNode(index2);
            last = this.getNode(index1);
        }
        if((index1 == 0 && index2 == theSize -1) ||(index1 == theSize -1 && index2 == 0))
        {   
            first.next.prev = last;
            last.prev.next = first;

            first.prev = last.prev;
            last.next = first.next;

            first.next = endMarker;
            endMarker.prev = first;
            last.prev = beginMarker;
            beginMarker.next = last;
        }

        else if(Math.abs(index1-index2) == 1)
        {
            first.next = last.next;
            last.prev = first.prev;
            first.prev = last;
            last.next = first;
            last.prev.next = last;
            first.next.prev = first;
        }

        else
        {
            Node<AnyType> tempNext = last.next;
            Node<AnyType> tempPrev = last.prev;

            last.next.prev = first;
            last.prev.next = first;
            first.prev.next = last;
            first.next.prev = last;

            last.next = first.next;
            last.prev = first.prev;
            first.next = tempNext;
            first.prev = tempPrev;
        }
}
public static void main( String [ ] args )
{
    MyLinkedList<Integer> lst = new MyLinkedList<>( );
    MyLinkedList<Integer> lst2 = new MyLinkedList<>( );

    for( int i = 0; i < 10; i++ )
            lst.add( i );
    System.out.println("Original List: " + lst);

    lst2 = lst.reverse();
    System.out.println("Original List: " + lst);
    System.out.println("Reversed List: " + lst2);
}

这是我的输出:

Original List: [ 0 1 2 3 4 5 6 7 8 9 ]
Original List: [ 9 8 7 6 5 4 3 2 1 0 ]
Reversed List: [ 9 8 7 6 5 4 3 2 1 0 ]

正如您所看到的，原始列表也被颠倒了。为什么会发生这种情况？

Answer 1

原因如下:

lst2 = lst.reverse();

您正在调用 reverse()上lst所以lst将会被逆转。然后将结果分配给 lst2这也将被保留。解决方案是深度复制 lst ，分配它lst2并调用

lst2.reverse();

而不是这个:MyLinkedList<AnyType> list = this;

试试这个:

for( int i = 0; i < 10; i++ )
    list.add( this.getNode(i) );