HashMap中的NULL键的Hashcode [英] Hashcode for NULL key in HashMap

问题描述

我只是看看Java中的HashMap和HashTable类之间的区别。在那里我发现一个区别，前者允许null键和后来没有特权的相同。
就HashMap的工作而言，我知道，它会调用hashcode方法来查找要放置该键值对的桶。这里提出了我的问题：
如何计算空值的哈希码，或者是否有null键的哈希码的默认值（如果是这样，请指定值）？

  public V put（K key，V value）{ 
 if（key == null）
 return putForNullKey（value）; 
 ... 
  

如果你看得更远，你会看到null总是去bin 0

I was just reading about the difference between HashMap and HashTable class in java. There I found a difference that former allow null key and later doesn't privileges for the same. As far as the working of HashMap is concern I know that, it calls hashcode method on key for finding the bucket in which that key value pair is to be placed. Here comes my question: How hashcode for a null value is computed or Is there any default value for hashcode of null key (if so please specify the value)?

解决方案

from HashMap:

public V put(K key, V value) {
   if (key == null)
      return putForNullKey(value);
   ...

and if you look further you will see that null always goes to bin 0

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