LinkedList源碼分析

geekidentity 發(fā)布于2019-08-16 15:21 / 548人閱讀

一、屬性及獲取屬性：

1、size

transient int size = 0;

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

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

獲取

public int size() {
    return size;
}

二、構(gòu)造函數(shù)

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

public LinkedList(Collection c) {
    this();
    addAll(c);
}

三、類

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

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

四、方法

1、Node

Node node(int index) {
    // assert isElementIndex(index);

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

*、linkFirst

/**
 * Links e as first element.
 */
private void linkFirst(E e) {
    final Node f = first;
    final Node newNode = new Node<>(null, e, f);
    first = newNode;
    if (f == null)
        last = newNode;
    else
        f.prev = newNode;
    size++;
    modCount++;
}

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

*、add、addFirst

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

linkLast

2、set

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

3、get

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

*、clear

public void clear() {
    // Clearing all of the links between nodes is "unnecessary", but:
    // - helps a generational GC if the discarded nodes inhabit
    //   more than one generation
    // - is sure to free memory even if there is a reachable Iterator
    for (Node x = first; x != null; ) {
        Node next = x.next;
        x.item = null;
        x.next = null;
        x.prev = null;
        x = next;
    }
    first = last = null;
    size = 0;
    modCount++;
}

*、Push Pop

public void push(E e) {
    addFirst(e);
}

public E pop() {
    return removeFirst();
}

*、node(int index)

Node node(int index) {
    // assert isElementIndex(index);

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