Java集合类-LinkedList分析

LinkedList的特点

非线程安全

支持序列化

双向链表

 

 

成员变量

transient int size = 0;
transient Node<E> first; // 指向第一个元素
transient Node<E> last; // 指向最后一个元素

链表结点，三个属性：元素、上一结点、下一结点

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;
    }
}

 

基本方法

增 add

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

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

 

删 remove

removeLast

public E removeLast() {
    final Node<E> l = last;
    if (l == null)
        throw new NoSuchElementException();
    return unlinkLast(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;
}

 remove

public E remove(int index) {
    checkElementIndex(index);
    return unlink(node(index));
}

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) { // index的结点是头结点
        first = next;
    } else {
        prev.next = next;
        x.prev = null;
    }

    if (next == null) { // index的结点是尾结点
        last = prev;
    } else {
        next.prev = prev;
        x.next = null;
    }

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

 

改 set

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


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;
    }
}

 

查找index位置结点的时候，判断在前半段还是后半段，然后从头结点或者尾结点进行遍历

查 get

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

 

扩容原理

增加新结点，将新结点联结进双链表

一些问题

 

参考

http://blog.csdn.net/ns_code/article/details/35787253