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Mastering Concurrency in Java: Overcoming HashMap Challenges with ConcurrentHashMap

The Java Trail
8 min readOct 30, 2024

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In concurrent programming, managing shared data structures is essential, especially when multiple threads access and modify resources simultaneously. Collections like HashMap work efficiently in single-threaded environments but face significant issues in a multithreaded context, particularly during modifications like put (insertion) or remove (deletion). These issues can lead to unpredictable behavior, such as infinite loops during resizing, and even data corruption.

To address these challenges, Java offers alternatives like Hashtable and the more advanced ConcurrentHashMap. ConcurrentHashMap provides thread safety with higher concurrency, making it suitable for shared, mutable data in multithreaded applications. This article examines the behavior of HashMap in multithreaded environments, the issues that arise, and how ConcurrentHashMap overcomes these limitations through segmentation, efficient resizing, and load factor management.

HashMap Challenges: Multithreaded Environments

HashMap is efficient in single-threaded scenarios but becomes problematic when used in multithreaded environments. This is especially true when threads attempt concurrent modifications, such as put (adding/updating a key-value pair) or remove

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The Java Trail
The Java Trail

Written by The Java Trail

Scalable Distributed System, Backend Performance Optimization, Java Enthusiast. (mazumder.dip.auvi@gmail.com Or, +8801741240520)

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