ArrayList与LinkedList实现比较

1 public class ArrayList<E> extends AbstractList<E>
2         implements List<E>, RandomAccess, Cloneable, java.io.Serializable
3 {
4     private transient Object[] elementData;
5 
6     private int size;
7     
8     /*其他参数和方法*/
9 }

 1 public class LinkedList<E>
 2     extends AbstractSequentialList<E>
 3     implements List<E>, Deque<E>, Cloneable, java.io.Serializable
 4 {
 5     private transient Entry<E> header = new Entry<E>(null, null, null);
 6     private transient int size = 0;
 7 
 8     /**
 9      * 构造器，构建空表
10      */
11     public LinkedList() {
12         header.next = header.previous = header;
13     }
14 
15     /*其他参数、方法*/
16 
17     /**
18     * LinkedList链表元素
19     */
20     private static class Entry<E> {
21     E element;
22     Entry<E> next;
23     Entry<E> previous;
24 
25     Entry(E element, Entry<E> next, Entry<E> previous) {
26         this.element = element;
27         this.next = next;
28         this.previous = previous;
29     }
30     }
31  
32     /**
33     * LinkedList获取第一个元素的方法实现
34     */
35     public E getFirst() {
36     if (size==0)
37         throw new NoSuchElementException();
38 
39     return header.next.element;
40     }
41 
42 }