Nuance of Java development

This blog is about Java development and describes in detail the most important topics.

Posts with tag «ConcurrentHashMap»


How to use ConcurrentHashMap in Java

Before Java 1.5, if you need Map implementation, which can be safely used in multithreading Java-application, you have only Hashtable or synchronized Map, because HashMap is NOT safe.

Introduction ConcurrentHashMap was presented as alternative to Hashtable in Java 1.5 as part of concurrency package. With ConcurrentHashMap, you have a better choice not only if it can be safely used in the concurrent multi-threaded environment but also provides better performance than Hashtable and synchronizedMap. ConcurrentHashMap performs better because it locks a part of Map. It allows concurred read operations and the same time maintains integrity by synchronizing write operations. In this article we will know: How ConcurrentHashMap is implemented in Java. Some important properties of ConcurrentHashMap. When to use ConcurrentHashMap. How ConcurrentHashMap is implemented ConcurrentHashMap was developed as alternative of Hashtable and support all functionality of Hashtable with additional ability, so called concurrency level. ConcurrentHashMap allows multiple readers to read simultaneously without using blocks. It becomes possible by separating Map to different parts and blocking only part of Map in updates. By default, concurrency level is 16, so Map is spitted to 16 parts and each part is managed by separated block. It means, that 16 threads can work with Map simultaneous Read more

March 29, 2019