LinkedList实现 - addAll()

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addAll()

addAll(index, c) 实现方式并不是直接调用add(index,e)来实现，主要是因为效率的问题，另一个是fail-fast中modCount只会增加1次；

1. 
   
2.     /**
   
3.      * Appends all of the elements in the specified collection to the end of
   
4.      * this list, in the order that they are returned by the specified
   
5.      * collection's iterator.  The behavior of this operation is undefined if
   
6.      * the specified collection is modified while the operation is in
   
7.      * progress.  (Note that this will occur if the specified collection is
   
8.      * this list, and it's nonempty.)
   
9.      *
   
10.      * @param c collection containing elements to be added to this list
    
11.      * @return {@code true} if this list changed as a result of the call
    
12.      * @throws NullPointerException if the specified collection is null
    
13.      */
    
14.     public boolean addAll(Collection<? extends E> c) {
    
15.         return addAll(size, c);
    
16.     }
    
17. 
    
18.     /**
    
19.      * Inserts all of the elements in the specified collection into this
    
20.      * list, starting at the specified position.  Shifts the element
    
21.      * currently at that position (if any) and any subsequent elements to
    
22.      * the right (increases their indices).  The new elements will appear
    
23.      * in the list in the order that they are returned by the
    
24.      * specified collection's iterator.
    
25.      *
    
26.      * @param index index at which to insert the first element
    
27.      *              from the specified collection
    
28.      * @param c collection containing elements to be added to this list
    
29.      * @return {@code true} if this list changed as a result of the call
    
30.      * @throws IndexOutOfBoundsException {@inheritDoc}
    
31.      * @throws NullPointerException if the specified collection is null
    
32.      */
    
33.     public boolean addAll(int index, Collection<? extends E> c) {
    
34.         checkPositionIndex(index);
    
35. 
    
36.         Object[] a = c.toArray();
    
37.         int numNew = a.length;
    
38.         if (numNew == 0)
    
39.             return false;
    
40. 
    
41.         Node<E> pred, succ;
    
42.         if (index == size) {
    
43.             succ = null;
    
44.             pred = last;
    
45.         } else {
    
46.             succ = node(index);
    
47.             pred = succ.prev;
    
48.         }
    
49. 
    
50.         for (Object o : a) {
    
51.             @SuppressWarnings("unchecked") E e = (E) o;
    
52.             Node<E> newNode = new Node<>(pred, e, null);
    
53.             if (pred == null)
    
54.                 first = newNode;
    
55.             else
    
56.                 pred.next = newNode;
    
57.             pred = newNode;
    
58.         }
    
59. 
    
60.         if (succ == null) {
    
61.             last = pred;
    
62.         } else {
    
63.             pred.next = succ;
    
64.             succ.prev = pred;
    
65.         }
    
66. 
    
67.         size += numNew;
    
68.         modCount++;
    
69.         return true;
    
70.     }
    

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原文链接：https://pdai.tech/md/java/collection/java-collection-LinkedList.html