JAVA数据结构——集合之LinkedList
分类:
IT文章
•
2023-11-07 17:37:57
LinkedList与ArrayList同继承自List接口，其与ArrayList的本质区别即是，ArrayList内置了一个数组，而LinkedList则内置了一个链表，其余所有的区别均衍生自两者的本质区别。
LinkedList与ArrayList的主要区别：
- LinkedList内置链表，ArrayList内置数组
- 因为链表和数组的差异，在执行add方法时，一旦ArrayList的空间不足会引起整个ArrayList的拷贝，效率较低，而LinkedList理论上是没有大小限制的
- 因为链表和数组的差异，在执行插入时，ArrayList的会引起部分空间拷贝（拷贝数据的多少取决于插入元素的位置），LinkedList则会执行遍历操作
- 其他差异，也基本由于结构的不同导致，随时补充
常用方法：
内部节点结构
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1 private static class Node<E> {
2 E item;
3 Node<E> next;
4 Node<E> prev;
5
6 Node(Node<E> prev, E element, Node<E> next) {
7 this.item = element;
8 this.next = next;
9 this.prev = prev;
10 }
11 }
private static class Node
数据结构
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1 transient int size = 0;
2
3 /**
4 * Pointer to first node.
5 * Invariant: (first == null && last == null) ||
6 * (first.prev == null && first.item != null)
7 */
8 transient Node<E> first;
9
10 /**
11 * Pointer to last node.
12 * Invariant: (first == null && last == null) ||
13 * (last.next == null && last.item != null)
14 */
15 transient Node<E> last;
结构变量
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1 /**
2 * 以参数集合构建新的LinkedList，构建过程调用addAll实现
3 */
4 public LinkedList(Collection<? extends E> c) {
5 this();
6 addAll(c);
7 }
8
9 /**
10 * 调用
11 */
12 public boolean addAll(Collection<? extends E> c) {
13 return addAll(size, c);
14 }
15
16 /**
17 * Inserts all of the elements in the specified collection into this
18 * list, starting at the specified position. Shifts the element
19 * currently at that position (if any) and any subsequent elements to
20 * the right (increases their indices). The new elements will appear
21 * in the list in the order that they are returned by the
22 * specified collection's iterator.
23 *
24 * @param index index at which to insert the first element
25 * from the specified collection
26 * @param c collection containing elements to be added to this list
27 * @return {@code true} if this list changed as a result of the call
28 * @throws IndexOutOfBoundsException {@inheritDoc}
29 * @throws NullPointerException if the specified collection is null
30 */
31 public boolean addAll(int index, Collection<? extends E> c) {
32 checkPositionIndex(index);
33
34 Object[] a = c.toArray();
35 int numNew = a.length;
36 if (numNew == 0)
37 return false;
38
39 Node<E> pred, succ;
40 if (index == size) {
41 succ = null;
42 pred = last;
43 } else {
44 succ = node(index);
45 pred = succ.prev;
46 }
47
48 for (Object o : a) {
49 @SuppressWarnings("unchecked") E e = (E) o;
50 Node<E> newNode = new Node<>(pred, e, null);
51 if (pred == null)
52 first = newNode;
53 else
54 pred.next = newNode;
55 pred = newNode;
56 }
57
58 if (succ == null) {
59 last = pred;
60 } else {
61 pred.next = succ;
62 succ.prev = pred;
63 }
64
65 size += numNew;
66 modCount++;
67 return true;
68 }
