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How to parse the Hashtable source code, in view of this problem, this article introduces the corresponding analysis and solution in detail, hoping to help more partners who want to solve this problem to find a more simple and feasible method.

Today we will analyze the underlying implementation of Hashtable. The mention of Hashtable may be unfamiliar to some people because it is not used very often. This is because Hashtable has been a collection class for a long time, because it exists in the JDK1.0 version. The HashMap collection is available after the Hashtable collection. It can also be understood that the HashMap collection is an optimized Hashtable. So their underlying implementation is almost the same, but they also have some differences to note, and they are all stored in a hash table. Now that we have mastered the underlying implementation of HashMap, it will be easier for us to analyze Hashtable, so this article will directly analyze the underlying source code of Hashtable and will not introduce the knowledge of hash tables. As with other collections, let's first look at the initialization of Hashtable.

Initialization

The above source code is the method that is called when the Hashtable collection is initialized, that is, when we create the Hashtable object through the default no-parameter constructor, the above code is executed. Since we have analyzed the source code in HashMap, we will not explain too much here. We will focus on the difference between Hashtable initialization and HashMap initialization.

As we analyzed in the HashMap article, when creating a HashMap object through a no-parameter constructor, only the load factor in HashMap is set to the default of0.75, and the initialization of the underlying array is not performed. In Hashtable, not only the default load factor is set to 0.75, but also the underlying array has been initialized. The default initialized array size is for 11.

Let's take a look at the underlying implementation logic of the put method in Hashtable.

Through the analysis of the above source code, we can get the following characteristics of Hashtable.

When we create a Hashtable object through the no-parameter construction method, the underlying array performs initialization and sets the array size to the default size of 11 and the load factor to the default value of 0.75

Null elements are not allowed to be saved in Hashtable, whether key or value

Hashtable cannot save the same key element. If the key of the element is the same, the value of the element that is later added to the Hashtable overrides the value of the element that already exists in the original Hashtable.

When Hashtable performs a rehash, it creates a new array that is 2 times larger than the original array + 1

In Hashtable, we find that the synchronization keyword synchronized is added to the method, which shows that Hashtable is a thread-safe collection class, and in multithreaded development, we can ensure the thread safety of the collection without adding additional synchronization code.

The answer to the question about how to parse the Hashtable source code is shared here. I hope the above content can be of some help to everyone. If you still have a lot of doubts to solve, you can follow the industry information channel to learn more about it.

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