Shulou(Shulou.com)06/02 Report--

This article mainly introduces the differences between ConcurrentHashMap1.7 and 1.8, which have a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand.

ConcurrentHashMap is a thread-safe and efficient HashMap.

Hashmap in a multithreaded environment, put operations will have an endless loop. HashTable is thread-safe and is implemented using hashmap's implementation method + sychronized.

HashEntry is a linked list that holds the hashcode and value values of key.

ConcurrentHashMap 1.7 is implemented using the segment array + HashEntry array. Segment inherits ReentrantLock. When looking for data, first calculate the hashcode through key and find the location in the segment. Locate the table in the current Segment to the HashEntry through the hashcode of the key, and then to the specific element.

1.7 has solved the concurrency problem, but when the HashEntry linked list is too large, the query efficiency is inefficient. Therefore, 1.8 mainly solves the problem of query efficiency. 1.8A great change has been made in the data structure of 1.7. after using the red-black tree, we can ensure the query efficiency (O (logn)), and even cancel the ReentrantLock and change it to synchronized, so we can see that the synchronized optimization is in place in the new version of JDK.

Thank you for reading this article carefully. I hope the article "what's the difference between ConcurrentHashMap1.7 and 1.8" shared by the editor will be helpful to you. At the same time, I also hope you will support us and pay attention to the industry information channel. More related knowledge is waiting for you to learn!

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