为什么哈希图中的空键总是转到第一个存储桶？

Question

What is the benefit? And why do we need particular methods for nulls like putForNullKey(V value) , getForNullKey() and similar? What is the benefit?

Answer 1

You can't calculate hashCode of a null key, so you have to put all the null keys in the same bucket. You might as well put them in the first bucket.

And you have specific methods for null keys since their logic is different than non-null keys. These methods are private anyway, so it shouldn't matter to the user of the HashMap . The public API is the same for null and non-null keys.