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This article will explain in detail what ConcurrentHashMap and HashTable are. The editor thinks it is very practical, so I share it with you as a reference. I hope you can get something after reading this article.

Non-thread-safe collections in java collection classes can be made thread-safe with synchronization wrappers, such as:

HashMap-> Collections.synchronizedMap (new HashMap ())

So if you compare Collections.synchronizedMap (new HashMap ()) with HashTable,

Which is more efficient? What other similar HashMap-HashTable are there? each

What about the efficiency?

In fact, Java collections use a lot of data structures. Java collection classes implemented with different data structures certainly have different performance in different situations. Here is a brief description of the efficiency of these two similar java collection classes under multi-threading (usually in terms of time):

First of all, Collections.synchronizedMap (new HashMap ()) and HashTable are synchronous sets, Collections.synchronizedMap uses synchronous block implementation, and HashTable uses synchronous method. In multithreaded environment, it is generally considered that synchronous block is better than synchronous method.

Secondly, when it comes to multithreading, thread safety is very important. these two synchronous sets are not a problem for some common simple operations, such as put, remove, get, etc., but for some compound operations, such as put and remove, iteration, etc., to ensure thread safety, you must add locks synchronously when you use them, that is, to ensure that operations like put and remove are atomic operations. Of course, the two Java collection classes are implemented by hash algorithm, and there will be no big difference in running efficiency. As mentioned earlier, they are all synchronous sets, that is to say, in multithreaded concurrent operations, no matter simple operations or compound operations, they are serial operations for thread safety, which will greatly reduce the efficiency of the program. So, concurrent set ConcurrentHashMap appears, which not only solves the concurrency problem, but also solves the efficiency problem.

Finally, it is recommended that you use ConcurrentHashMap in multithreading and replace the two synchronous collections you mentioned.

The problem of fish and bear's paw.

For example, the bidding system will not be too large, and the concurrency will not be too high.

At this time, you don't have to think about space management and other issues, speed and efficiency are the top priority.

And if it's a banking project, if you choose between efficiency and security, if you're a programmer, how do you choose?

This is the end of the article on "what are ConcurrentHashMap and HashTable". I hope the above content can be helpful to you so that you can learn more knowledge. if you think the article is good, please share it for more people to see.

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