Java8中HashMap扩容算法小计

1 final Node<K,V>[] resize() {
2     // ...省略不重要的
3 }

 1 for (int j = 0; j < oldCap; ++j) {
 2     Node<K,V> e;
 3     if ((e = oldTab[j]) != null) {
 4         oldTab[j] = null;
 5         if (e.next == null)
 6             newTab[e.hash & (newCap - 1)] = e;
 7         else if (e instanceof TreeNode)
 8             ((TreeNode<K,V>)e).split(this, newTab, j, oldCap);
 9         else { // preserve order
10             Node<K,V> loHead = null, loTail = null;
11             Node<K,V> hiHead = null, hiTail = null;
12             Node<K,V> next;
13             do {
14                 next = e.next;
15                 if ((e.hash & oldCap) == 0) {
16                     if (loTail == null)
17                         loHead = e;
18                     else
19                         loTail.next = e;
20                     loTail = e;
21                 }
22                 else {
23                     if (hiTail == null)
24                         hiHead = e;
25                     else
26                         hiTail.next = e;
27                     hiTail = e;
28                 }
29             } while ((e = next) != null);
30             if (loTail != null) {
31                 loTail.next = null;
32                 newTab[j] = loHead;
33             }
34             if (hiTail != null) {
35                 hiTail.next = null;
36                 newTab[j + oldCap] = hiHead;
37             }
38         }
39     }
40 }
41 
42 
43 final V putVal(int hash, K key, V value, boolean onlyIfAbsent, boolean evict) {
44     // ...省略不重要的
45     if ((p = tab[i = (n - 1) & hash]) == null)
46         tab[i] = newNode(hash, key, value, null);
47     else {
48     // ...省略不重要的
49 }