1 public class MyLinkedHashMap<K, V> extends MyHashMap<K, V> {
2 private boolean accessOrder;
3
4 private Entry<K, V> header;
5
6 public V get(K k) {
7 Entry<K, V> e = (Entry<K, V>) getEntry(k);
8 if (e == null) {
9 return null;
10 }
11 e.recordAccess(this);
12 return e.value;
13 }
14
15 @Override
16 void addEntry(K k, V v, int index) {
17 MyHashMap.Entry<K, V> old = table[index];
18 Entry<K, V> e = new Entry<K, V>(k, v, old);
19 table[index] = e;
20 e.addBefore(header);
21 size++;
22 Entry<K, V> eldest = header.after;
23 /**
24 * 如果用於表示LRU算法的缓存，需覆盖removeEldestEntry，删除最旧条目同时返回true
25 */
26 if (removeEldestEntry(eldest)) {
27 removeEntryForKey(eldest.key);
28 } else {
29 if (size >= threshold) {
30 resize(2 * table.length);
31 }
32 }
33 }
34
35 boolean removeEldestEntry(Entry<K, V> e) {
36 return false;
37 }
38
39 private static class Entry<K, V> extends MyHashMap.Entry<K, V> {
40 Entry<K, V> before, after;
41
42 public Entry(K k, V v, MyHashMap.Entry<K, V> n) {
43 super(k, v, n);
44 // TODO Auto-generated constructor stub
45 }
46
47 private void remove() {
48 before.after = after;
49 after.before = before;
50 }
51
52 private void addBefore(Entry<K, V> existingEntry) {
53 after = existingEntry;
54 before = existingEntry.before;
55 after.before = this;
56 before.after = this;
57 }
58
59 void recordAccess(MyHashMap<K, V> m) {
60 MyLinkedHashMap<K, V> lm = (MyLinkedHashMap<K, V>) m;
61 if (lm.accessOrder) {
62 remove();
63 addBefore(lm.header);
64 }
65 }
66
67 }
68
69 }
