Shulou(Shulou.com)06/01 Report--

In this issue, the editor will bring you about why the Hashtable in Java should be named in lowercase rather than hump. The article is rich in content and analyzes and narrates it from a professional point of view. I hope you can get something after reading this article.

Hashtable and HashMap are two data structure knowledge points that must be asked in the interview. Today let's talk about Hashtable!

Before we begin, let me ask you a question: why is the T in Hashtable not capitalized? I have been googling Baidu for a long time without a reasonable answer! According to the comments of foreign netizens, Hashtable did not follow the hump command because of the bug generated when the programmer wrote it, although sun noticed the problem later. But considering the historical compatibility, I chose to keep it as it is!

When it comes to Hashtable, there are only a few points that you can talk about:

Compared to HashMap,Hashtable, it is thread safe. Because the synchronized keyword is added to several important methods of Hashtable.

Neither key nor value of Hashtable can be null. HashMap allows at most the key of one record to be null and the value of multiple records to be null.

Hashtable inherits from the Dictionary class, and HashMap inherits from the AbstractMap class.

Hashtable is obsolete and can be replaced with ConcurrentHashMap, which can be found in the comments in the Hashtable source code.

Both Hashtable and HashMap use Iterator. For historical reasons, Hashtable also uses the Enumeration approach.

Hashtable uses the object's hashCode directly. HashMap recalculates the hash value.

The initial size of the hash array in HashTable is 11, which is incremented by old*2+1. The default size of the hash array in HashMap is 16, and it must be an exponent of 2.

HashMap has two methods, containsvalue and containsKey, and Hashtable uses the contains method.

Most of the HashMap implementations are the same, and there's nothing to say. Can be thought of as a lightweight implementation of Hashtable. Since most of the Hashtable and HashMap implementations are the same, there is nothing to say. In addition, Hashtable is no longer recommended, so I suggest you stop using it and use ConcurrentHashMap instead.

The above is why the Hashtable in the Java shared by the editor should be named in lowercase instead of the hump. If you happen to have similar doubts, please refer to the above analysis to understand. If you want to know more about it, you are welcome to follow the industry information channel.

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