双链表-java

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//双链表
class DLinkList
{
    // 结点类
    class Node
    {
        int data;
        Node prior; // 前指针
        Node next; // 后指针

        Node()
        {
        }

        Node(int data)
        {
            this.data = data;
        }
    }

    Node first;
    Node r;

    public DLinkList()
    {
        first = new Node();
        r = first;
    }

    public DLinkList(int[] a)
    {
        this();
        for (int i = 0; i < a.length; i++)
        {
            Node n = new Node(a[i]);
            r.next = n;
            n.prior = r;
            r = n;
        }
    }

    // 添加结点，动四根线
    public void AddNodeI(int i, int data)
    {
        if (i <= 0)
        {
            System.out.println("Error: Out of index");
        } else
        {
            Node current = first;
            int j = 0;
            while (j < i - 1 && current != null)
            {
                j++;
                current = current.next;
            }
            if (current == null || current.next == null)
            {
                System.out.println("Error:Out of index!");
            } else
            {
                Node n = new Node(data);
                n.next = current.next;
                current.next.prior = n;
                n.prior = current;
                current.next = n;
            }
        }
    }

    // 删除结点，动两根线
    public void DeleteNodeI(int i)
    {
        if (i <= 0)
        {
            System.out.println("Error:Out of index");
        } else
        {
            Node current = first;
            int j = 0;
            while (j < i - 1 && current != null)
            {
                j++;
                current = current.next;
            }
            if (current == null || current.next == null)
            {
                System.out.println("Error:Out of index");
            } else
            {
                Node currentNext = current.next; // !!!!!!注意，先提出current.next保存到新引用中
                if (currentNext.next != null)
                {
                    current.next = currentNext.next;
                    currentNext.next.prior = current;
                } else
                {
                    current.next = null;
                    currentNext.prior = null;
                    r = current;
                }
            }
        }
    }

    // 正向打印链表所有元素
    public void DispListF()
    {
        Node current = first.next;
        System.out.print("正向：");
        while (current != null)
        {
            System.out.print(current.data + " ");
            current = current.next;
        }
        System.out.println();
    }

    // 反向打印链表所有元素
    public void DispListR()
    {
        Node current = r;
        System.out.print("反向：");
        while (current != null && current != first)
        {
            System.out.print(current.data + " ");
            current = current.prior;
        }
        System.out.println();
    }
}

public class MyDLinkList
{
    public static void main(String args[])
    {
        int[] a =
        { 1, 2, 3, 4, 5 };
        System.out.println("实例化链表并赋值数组a={1,2,3,4,5}");
        DLinkList dl = new DLinkList(a);
        dl.DispListF();
        dl.DispListR();
        System.out.println("在第3位添加32");
        dl.AddNodeI(3, 32);
        dl.DispListF();
        dl.DispListR();
        System.out.println("删除第3位的结点");
        dl.DeleteNodeI(3);
        dl.DispListF();
        dl.DispListR();
    }
}

输出：
实例化链表并赋值数组a={1,2,3,4,5}
正向：1 2 3 4 5
反向：5 4 3 2 1
在第3位添加32
正向：1 2 32 3 4 5
反向：5 4 3 32 2 1
删除第3位的结点
正向：1 2 3 4 5
反向：5 4 3 2 1