链表的遍历，查询和修改

public class LinkedList<E> {
    private class Node {
        public E e;
        public Node next;

        public Node(E e, Node next) {
            this.e = e;
            this.next = next;
        }

        public Node(E e) {
            this.e = e;
            this.next = null;
        }

        public Node() {
            this.e = null;
            this.next = null;
        }

        @Override
        public String toString() {
            return e.toString();
        }
    }

    private Node dummyHead;
    int size;

    public LinkedList() {
        dummyHead = new Node(null, null);
        size = 0;
    }

    //可以尝试传进来一个数组，把数组转换成链表的构造函数

    //获取链表中的元素个数
    public int getSize() {
        return size;
    }

    //返回链表是否为空
    public boolean isEmpty() {
        return size == 0;
    }

    //在链表头添加新的元素e
    public void addFirst(E e) {
        add(0,e);
    }

    //在链表的index(o-based)位置添加新的元素e
    //在链表中不是一个常用的操作，练习用:)
    public void add(int index, E e) {
        if (index < 0 || index > size)
            throw new IllegalArgumentException("Add failed.Illegal index.");

        Node prev = dummyHead;
        for (int i = 0; i < index; i++) {
            prev = prev.next;
        }
        prev.next = new Node(e, prev.next);
        size++;

    }

    //在链表末尾添加新的元素e
    public void addLast(E e) {
        add(size, e);
    }

    //获得链表的第index(o-based)个位置的元素e
    //在链表中不是一个常用的操作，练习用:)
    public E get(int index){
        if (index < 0 || index > size)
            throw new IllegalArgumentException("Get failed.Illegal index.");

        Node cur = dummyHead.next;
        for(int i = 0; i < index ; i ++)
            cur = cur.next;
        return cur.e;
    }

    //获取链表的第一个元素
    public E getFirst(){
        return get(0);
    }

    //获取链表的最后一个元素
    public E getLast(){
        return get(size - 1);
    }

    //修改链表的在第index(o-based)个位置的元素为e
    //在链表中不是一个常用的操作，练习用:)
    public void set(int index,E e){
        if (index < 0 || index > size)
            throw new IllegalArgumentException("Set failed.Illegal index.");
        Node cur = dummyHead.next;
        for (int i = 0; i < index; i++) {
            cur = cur.next;
        }
        cur.e = e;
    }

    //查找链表中是否存在元素e
    public boolean contains(E e){

        Node cur = dummyHead.next;
        while( cur != null){
            if(cur.e.equals(e)){
                return true;
            }
            cur = cur.next;
        }
        return false;
    }

    @Override
    public String toString(){
        StringBuilder res = new StringBuilder();

        Node cur = dummyHead.next;
        while( cur != null){
            res.append(cur + "->");
            cur = cur.next;
        }
        res.append("null");

        return res.toString();
    }
}

Main方法运行

public class Main {
    public static void main(String[] args) {
        LinkedList<Integer> linkedList = new LinkedList<>();
        for(int i = 0 ; i < 5; i ++){
            linkedList.addFirst(i);
            System.out.println(linkedList);
        }

        linkedList.add(2,666);
        System.out.println(linkedList);
    }
}

运行结果：

0->null
1->0->null
2->1->0->null
3->2->1->0->null
4->3->2->1->0->null
4->3->666->2->1->0->null