为什么我们需要检查哈希码两次？[重复]-Whydoweneedtocheckhashcodetwice?[duplicate]

This is the code of HashMap.java (docjar). Hash for key is calculated on line 431. This helps to fetch the index i on line 432. This all the entries at that index should have the same hash. Why is the check for hash equality made again on line 440 ? (if (e.hash == hash )

这是HashMap.java（docjar）的代码。密钥的哈希值在第431行计算。这有助于在第432行获取索引i。该索引处的所有条目应具有相同的哈希值。为什么在第440行再次检查哈希等式？ （if（e.hash == hash）

private void putForCreate(K key, V value) {
  430           int hash = (key == null) ? 0 : hash(key.hashCode());
  431           int i = indexFor(hash, table.length);
  432   
  433           /**
  434            * Look for preexisting entry for key.  This will never happen for
  435            * clone or deserialize.  It will only happen for construction if the
  436            * input Map is a sorted map whose ordering is inconsistent w/ equals.
  437            */
  438           for (Entry e = table[i]; e != null; e = e.next) {
  439               Object k;
  440               if (e.hash == hash &&
  441                   ((k = e.key) == key || (key != null && key.equals(k)))) {
  442                   e.value = value;
  443                   return;
  444               }
  445           }
  446   
  447           createEntry(hash, key, value, i);
  448       }

1 个解决方案