双向链表

package com.cqu.Thread;

public class DLLNode {
    private int data;
    private DLLNode next;
    private DLLNode previous;
    public DLLNode(int data) {
        this.data=data;
    }
    public int getData() {
        return data;
    }
    public void setData(int data) {
        this.data = data;
    }
    public DLLNode getNext() {
        return next;
    }
    public void setNext(DLLNode next) {
        this.next = next;
    }
    public DLLNode getPrevious() {
        return previous;
    }
    public void setPrevious(DLLNode previous) {
        this.previous = previous;
    }
    int getDLLLength(DLLNode headNode) {
        int size=0;
        DLLNode currentNode=headNode;
        while(currentNode!=null) {
            size++;
            currentNode=currentNode.next;
        }
        return size;
    }
    DLLNode DLLInsert(DLLNode headNode,DLLNode nodeToInsert,int position) {
        if(headNode==null) {
            return nodeToInsert;
        }
        int size=getDLLLength(headNode);
        if(position>size+1||position<1) {
            System.out.println("position of nodetoinsert is invalid"+"the valid inputs are 1 to"+(size+1));
            return headNode;
        }
        if(position==1) {//链表的开头插入
            nodeToInsert.setNext(headNode);
            headNode.setPrevious(nodeToInsert);
            return nodeToInsert;
        }else {//在链表中间或末尾插入
            DLLNode previousNode=headNode;
            int count=1;
            while(count<position-1) {
                previousNode=previousNode.getNext();
                count++;
            }
            DLLNode currentNode=previousNode.getNext();
            nodeToInsert.setNext(currentNode);
            if(currentNode!=null) {
                currentNode.setPrevious(nodeToInsert);
            }
            previousNode.setNext(nodeToInsert);
            nodeToInsert.setPrevious(previousNode);
        }
        return headNode;
        
    }
    DLLNode DLLDelete(DLLNode headNode,int position) {
        int size=getDLLLength(headNode);
        if(position>size||position<1) {
            System.out.println("position of node to delete is invalid,the valid inputs are 1 to"+size);
            return headNode;
        }
        if(position==1) {
            DLLNode currentNode=headNode.getNext();
            headNode=null;
            currentNode.setPrevious(null);
            return currentNode;
        }else {
            DLLNode previousNode=headNode;
            int count=1;
            while(count<position-1) {
                previousNode=previousNode.getNext();
                count++;
            }
            DLLNode currentNode=previousNode.getNext();
            DLLNode laterNode=currentNode.getNext();
            previousNode.setNext(laterNode);
            if(laterNode!=null) {
                laterNode.setPrevious(previousNode);
            }
            currentNode=null;
        }
        return headNode;
    }
}