Java实现双向链表

package 链表;

public class DoubleLinkedListDemo {
    public static void main(String[] args) {
        DoubleLinkList doubleLinkList = new DoubleLinkList();
        doubleLinkList.add(1);
        doubleLinkList.add(4);
        doubleLinkList.add(2);
        doubleLinkList.add(3);
        doubleLinkList.add(4);
        doubleLinkList.show();
        System.out.println("=========================");
        doubleLinkList.update(2, 2);
        doubleLinkList.show();
        System.out.println("=========================");
        doubleLinkList.delete(3);
        doubleLinkList.show();
        System.out.println("=========================");
        doubleLinkList.add(5,5);
        doubleLinkList.show();
        System.out.println("=========================");
    }

}

@SuppressWarnings({"all"})
class DoubleLinkList {
    private DoubleLinkedListNode headNode = new DoubleLinkedListNode(0, null);

    
    public void add(int val) {
        DoubleLinkedListNode temp = headNode;
        while (temp.nextNode != null)
            temp = temp.nextNode;
        temp.nextNode = new DoubleLinkedListNode(val, temp);
        //插入节点后，链表长度+1
        headNode.val++;

    }

    
    public void add(int val, int loc) {
        DoubleLinkedListNode temp = headNode;
        for (int i = 1; i < loc; i++) {
            if (temp.nextNode == null)
                break;
            temp = temp.nextNode;
        }
        DoubleLinkedListNode newNode = new DoubleLinkedListNode(val, temp);
        newNode.preNode = temp;
        if (temp.nextNode != null)
            newNode.nextNode = temp.nextNode;
        temp.nextNode = newNode;
        headNode.val++;
    }


    
    public void delete(int loc) {
        if (loc > headNode.val)
            throw new RuntimeException("超出链表长度");
        DoubleLinkedListNode temp = headNode;
        for (int i = 1; i <= loc; i++)
            temp = temp.nextNode;
        temp.preNode.nextNode = temp.nextNode;
        //若删除节点是最后一个节点，会有空指针异常
        if (temp.nextNode != null)
            temp.nextNode.preNode = temp.preNode;
        headNode.val--;
    }


    
    public void update(int val, int loc) {

        DoubleLinkedListNode temp = headNode.nextNode;
        for (int i = 1; i < loc; i++)
            temp = temp.nextNode;
        temp.val = val;

    }


    
    public void show() {
        if (headNode.nextNode == null) {
            System.out.println("链表为空！");
            return;
        }
        DoubleLinkedListNode temp = headNode.nextNode;
        while (temp != null) {
            System.out.print(temp.val + "  ");
            temp = temp.nextNode;
        }
        System.out.println();
    }


    
    public int getLength() {
        return headNode.val;
    }
}



class DoubleLinkedListNode {
    public int val;
    public DoubleLinkedListNode preNode;
    public DoubleLinkedListNode nextNode;

    public DoubleLinkedListNode(int val, DoubleLinkedListNode preNode) {
        this.val = val;
        this.nextNode = null;
        this.preNode = preNode;
    }

    @Override
    public String toString() {
        return "DoubleLinkedListNode{" +
                "val=" + val +
                ", preNode=" + preNode +
                ", nextNode=" + nextNode +
                '}';
    }
}