针对当前热议的hashmap 中 hash 函数怎么是是实现的？话题，我们进行了深入调研和信息整合，力求为您呈现全面客观的内容分析。
HashMap是对数据结构中哈希表(Hash
Table)的实现，Hash表又叫散列表。Hash表是根据关键码Key来访问其对应的值Value的数据结构，它通过一个映射函数把关键码映射到表中一个位置来访问该位置的值，从而加快查找的速度。这个映射函数叫做Hash函数，存放记录的数组叫做Hash表。
在Java中，HashMap的内部实现结合了链表和数组的优势，链接节点的数据结构是Entry<k,v>，每个Entry对象的内部又含有指向下一个Entry类型对象的引用，如以下代码所示：
static
class
Entry<K,V>
implements
Map.Entry<K,V>
{
final
K
key;
V
value;
Entry<K,V>
next;
//Entry类型内部有一个自己类型的引用，指向下一个Entry
final
int
hash;
...
}
在HashMap的构造函数中可以看到，Entry表被申明为了数组，如以下代码所示：
public
HashMap()
{
this.loadFactor
=
DEFAULT_LOAD_FACTOR;
threshold
=
(int)(DEFAULT_INITIAL_CAPACITY
*
DEFAULT_LOAD_FACTOR);
table
=
new
Entry[DEFAULT_INITIAL_CAPACITY];
init();
}
在以上构造函数中，默认的DEFAULT_INITIAL_CAPACITY值为16，DEFAULT_LOAD_FACTOR的值为0.75。
当put一个元素到HashMap中去时，其内部实现如下：
public
V
put(K
key,
V
value)
{
if
(key
==
null)
return
putForNullKey(value);
int
hash
=
hash(key.hashCode());
int
i
=
indexFor(hash,
table.length);
...
}
歌曲：《Hush Hush》
歌手：Pussycat Dolls（“小猫咪”）
具体歌词：
I never needed you to be strong
I never needed you for pointing out my wrongs
I never needed pain, I never needed strain
My love for you is strong enough you should have known
I never needed you for judgment
I never needed you to question what I spend
I never ask for help
I take care of myself
I don’t why you think you got a hold on me
And it’s a little late for conversations
There isn’t anything for you to say
And my eyes hurt, hands shiver
So look at me and listen to me because…
I don’t want to stay another minute
I don’t want you to say a single word
Hush hush
Hush hush
There is no other way, I get the final say
Because…
I don’t want to, do this any longer
I don’t want you, theres nothing left to say
Hush hush
Hush hush
I’ve already spoken, our love is broken
Baby hush hush
I never needed your corrections
On everything from how I act to what I say
I never needed words I never needed hurts
I never needed you to be there everyday
I’m sorry for the way I let go
From everything I wanted when you came along
But I am never beaten, broken not defeated
I know next to you is not where I belong
And it’s a little late for explanations
There isn’t anything that you can do
And my eyes hurt, hands shiver
So you will listen when I say baby…
I don’t want to stay another minute
I don’t want you to say a single word
Hush hush
Hush hush
There is no other way, I get the final say
Because…
I don’t want to do this any longer
I don’t want you there’s nothing left to say
Hush hush
Hush hush
I’ve already spoken, our love is broken
Baby hush hush
No more words
No more lies
No more crying
No more pain
No more hurt
No more trying
I don’t want to stay another minute
I don’t want you to say a single word
Hush hush
Hush hush
There is no other way, I get the final say
Because…
I don’t want to, do this any longer
I don’t want you, theres nothing left to say
Hush hush
Hush hush
I’ve already spoken, our love is broken
Baby hush hush
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