Java数据结构--跟着api学数据结构--LinkedList

LinkedList:双向链表实现

public class LinkedList<E>
extends AbstractSequentialList<E>
implements List<E>, Deque<E>, Cloneable, java.io.Serializable
{
transient int size = 0;

/**
* Pointer to first node.
* Invariant: (first == null && last == null) ||
* (first.prev == null && first.item != null)
*/
transient Node<E> first;

/**
* Pointer to last node.
* Invariant: (first == null && last == null) ||
* (last.next == null && last.item != null)
*/
transient Node<E> last;

/**
* Constructs an empty list.
*/
public LinkedList() {
}

/**
* Constructs a list containing the elements of the specified
* collection, in the order they are returned by the collection's
* iterator.
*
* @param c the collection whose elements are to be placed into this list
* @throws NullPointerException if the specified collection is null
*/
public LinkedList(Collection<? extends E> c) {
this();
addAll(c);
}

Node:

private static class Node<E> {
E item;
Node<E> next;<pre name="code" class="java"> /**
* Links e as first element.
*/
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++;
}

/**
* Links e as last element.
*/
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++;
}

/**
* Inserts element e before non-null Node succ.
*/
void linkBefore(E e, Node<E> succ) {
// assert succ != null;
final Node<E> pred = succ.prev;
final Node<E> newNode = new Node<>(pred, e, succ);
succ.prev = newNode;
if (pred == null)
first = newNode;
else
pred.next = newNode;
size++;
modCount++;
}


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

    /**

     * Unlinks non-null first node f.

     */

    private E unlinkFirst(Node<E> f) {

        // assert f == first && f != null;

        final E element = f.item;

        final Node<E> next = f.next;

        f.item = null;

        f.next = null; // help GC

        first = next;

        if (next == null)

            last = null;

        else

            next.prev = null;

        size--;

        modCount++;

        return element;

    }

    /**

     * Unlinks non-null last node l.

     */

    private E unlinkLast(Node<E> l) {

        // assert l == last && l != null;

        final E element = l.item;

        final Node<E> prev = l.prev;

        l.item = null;

        l.prev = null; // help GC

        last = prev;

        if (prev == null)

            first = null;

        else

            prev.next = null;

        size--;

        modCount++;

        return element;

    }

    /**

     * Unlinks non-null node x.

     */

    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;

    }

    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;

    }

    /**

     * Returns the (non-null) Node at the specified element index.

     */

    Node<E> node(int index) {//通过链表遍历到特定的元素

        // 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;

        }

    }