LinkedList具体实现

LinkedL是基于链表结构的一种List实现

数据结构

LinkedList是基于链表结构的一种List实现,在remove, add这些操作上有先天性的优势

    transient int size = 0;
    transient Node<E> first; //链表的头指针
    transient Node<E> last; //尾指针
    //存储对象的结构 Node, LinkedList的内部类
    private static class Node<E> {
        E item;
        Node<E> next; // 指向下一个节点
        Node<E> prev; //指向上一个节点

        Node(Node<E> prev, E element, Node<E> next) {
            this.item = element;
            this.next = next;
            this.prev = prev;
        }
    }

链表增加元素

    // 在连表头添加元素, 简单的链表操作
     private void linkFirst(E e) {
        final Node<E> f = first;
        final Node<E> newNode = new Node<>(null, e, f);
        first = newNode;
        if (f == null)
            last = newNode;
        else
            f.prev = newNode;
        size++;
        modCount++;
    }

    //添加尾节点什么的都类似就不多赘述

链表删除元素

    //删除节点, 关键点就是x.prev.next = x.next; x.next.prev = x.prev; 其余删除方法都类似
    E unlink(Node<E> x) {
        // assert x != null;
        final E element = x.item;
        final Node<E> next = x.next;
        final Node<E> prev = x.prev;

        if (prev == null) {
            first = next;
        } else {
            prev.next = next;
            x.prev = null;
        }

        if (next == null) {
            last = prev;
        } else {
            next.prev = prev;
            x.next = null;
        }

        x.item = null;
        size--;
        modCount++;
        return element;
    }

查询某个元素

    //代码也很简单; 遍历整个链表
    public int indexOf(Object o) {
        int index = 0;
        if (o == null) {
            for (Node<E> x = first; x != null; x = x.next) {
                if (x.item == null)
                    return index;
                index++;
            }
        } else {
            for (Node<E> x = first; x != null; x = x.next) {
                if (o.equals(x.item))
                    return index;
                index++;
            }
        }
        return -1;
    }

获取index的元素

    //跟indexof()类似
    Node<E> node(int index) {
        // assert isElementIndex(index);

        if (index < (size >> 1)) {
            Node<E> x = first;
            for (int i = 0; i < index; i++)
                x = x.next;
            return x;
        } else {
            Node<E> x = last;
            for (int i = size - 1; i > index; i--)
                x = x.prev;
            return x;
        }
    }