LinkedList源码（基础代码）

LinkedList是由一个一个节点连接起来的链表

private static class Node<E> {
        E item;
        Node<E> next;
        Node<E> prev;

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

增

public boolean add(E e) {
        linkLast(e);
        return true;
    }

public void addFirst(E e) {
        linkFirst(e);
    }
    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++;
    }
    public void addLast(E e) {
        linkLast(e);
    }
    void linkLast(E e) {
        final Node<E> l = last;
        final Node<E> newNode = new Node<>(l, e, null);
        last = newNode;
        if (l == null)
            first = newNode;
        else
            l.next = newNode;
        size++;
        modCount++;
    }

删

public boolean remove(Object o) {
        if (o == null) {
            for (Node<E> x = first; x != null; x = x.next) {
                if (x.item == null) {
                    unlink(x);
                    return true;
                }
            }
        } else {
            for (Node<E> x = first; x != null; x = x.next) {
                if (o.equals(x.item)) {
                    unlink(x);
                    return true;
                }
            }
        }
        return false;
    }
    
    public E remove(int index) {
        checkElementIndex(index);
        return unlink(node(index));
    }

改

public E set(int index, E element) {
        checkElementIndex(index);
        Node<E> x = node(index);
        E oldVal = x.item;
        x.item = element;
        return oldVal;
    }

查

public E get(int index) {
        checkElementIndex(index);
        return node(index).item;
    }

其他

// 检索出第一个元素，但不取出
    public E peek() {
        final Node<E> f = first;
        return (f == null) ? null : f.item;
    }
    // 检索出第一个元素，同时取出
    public E poll() {
        final Node<E> f = first;
        return (f == null) ? null : unlinkFirst(f);
    }