整体框架

IMyLinkedList接口

这个接口用来存放所有方法，之后用MyLinkedList来实现这个接口，重写里面的方法

public interface IMyLinkedList {
    //头插法
    public void addFirst(int data);
    //尾插法
    public void addLast(int data);
    //任意位置插入,第一个数据节点为0号下标
    public void addIndex(int index,int data);
    //查找是否包含关键字key是否在单链表当中
    public boolean contains(int key);
    //删除第一次出现关键字为key的节点
    public void remove(int key);
    //删除所有值为key的节点
    public void removeAllKey(int key);
    //得到链表的长度
    public int size();
    //打印链表
    public void display();
    //释放链表
    public void clear();
}

IndexNotLegalException异常类

IndexNotLegalExceprion异常类用来判断index是否合法

public class IndexNotLegalException extends RuntimeException{
    public IndexNotLegalException() {
    }

    public IndexNotLegalException(String msg) {
        super(msg);
    }
}

MyLinkedList类

成员变量(节点信息)

static class ListNode {
        public int val;
        public ListNode prev;
        public ListNode next;
        public ListNode (int val){
            this.val = val;
        }
    }

    public ListNode head;
    public ListNode last;

addFirst(头插)

public void addFirst(int data) {
        ListNode newNode = new ListNode(data);
        if(head == null){
            head = last = newNode;
        }else{
            newNode.next = head;
            head.prev = newNode;
            head = newNode;
        }
    }

addLast(尾插)

public void addLast(int data) {
        ListNode newNode = new ListNode(data);
        if(head == null){
            head = last = newNode;
        }else{
            newNode.prev = last;
            last.next = newNode;
            last = newNode;
        }

    }

在指定位置插入数据

public void addIndex(int index, int data) {
        //判断index的合法性
        try{
            checkIndex(index);
        }catch(IndexNotLegalException e){
            e.printStackTrace();
        }
        if(index == 0){
            addFirst(data);
            return;
        }
        if(index == size()){
            addLast(data);
            return;
        }
        ListNode newNode = new ListNode(data);
        ListNode cur = head;
        while(index != 0){
            cur = cur.next;
            index--;
        }
        newNode.next = cur;
        newNode.prev = cur.prev;
        cur.prev.next = newNode;
        cur.prev = newNode;
    }
    private void checkIndex(int index){
        if(index<0 || index>size()){
            throw new IndexNotLegalException("Index不合法...");
        }
    }

判断是否存在

public boolean contains(int key) {
        ListNode cur = head;
        while(cur != null){
            if(cur.val == key){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

移除第一个相等的节点

public void remove(int key) {
        ListNode cur = head;
        if(head.val == key && head == last){
            head = last = null;
            return;
        }
        //如果删除的在head节点
        if(head.val == key){
            head = head.next;
            head.prev = null;
            return;
        }
        while(cur != null){
            if(cur.val == key){
                cur.prev.next = cur.next;
                if(cur.next == null){
                    last = cur.prev;
                    break;
                }
                cur.next.prev = cur.prev;
            }
            cur = cur.next;
        }
    }

移除所有相等的节点

public void removeAllKey(int key) {
        ListNode cur = head;
        if(head.val == key && head == last){
            head = last = null;
            return;
        }
        //如果删除的在head节点
        if(head.val == key){
            head = head.next;
            head.prev = null;
        }
        while(cur != null){
            if(cur.val == key){
                cur.prev.next = cur.next;
                if(cur.next == null){
                    last = cur.prev;
                    break;
                }
                cur.next.prev = cur.prev;
            }
            cur = cur.next;
        }
    }

链表的长度

 public int size() {
        int count = 0;
        ListNode cur = head;
        while (cur != null) {
            count++;
            cur = cur.next;
        }
        return count;
    }

打印链表

    public void display() {
        ListNode cur = head;
        while (cur != null) {
            System.out.print(cur.val + " ");
            cur = cur.next;
        }
        System.out.println();
    }

释放回收链表

public void clear() {
        ListNode cur = head;
        while(cur != null){
            ListNode curN = cur.next;
            cur.prev = null;
            cur.next = null;
            cur = curN;
        }
    }