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What are the differences between a HashMap and a Hash table in c#?

Revati S Misra22318-Aug-2023

What are the differences between a HashMap and a Hash table in Java?

c#c# java hashtable 
Updated on 19-Aug-2023
Revati S Misra

Revati S Misra

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Aryan Kumar

Aryan Kumar

19-Aug-2023

The main differences between a hashmap and a hashtable in C# are:

  • Synchronization: A hashmap is not synchronized, while a hashtable is synchronized. This means that a hashmap can be accessed by multiple threads at the same time, while a hashtable can only be accessed by one thread at a time.
  • Null values: A hashmap allows null values for both keys and values, while a hashtable does not allow null values for keys.
  • Performance: A hashmap is generally faster than a hashtable, but it can also be less memory efficient.

Here is a table summarizing the differences between hashmaps and hashtables in C#:

FeatureHashMapHashtable
SynchronizationNot synchronizedSynchronized
Null valuesAllows null values for keys and valuesDoes not allow null values for keys
PerformanceGenerally fasterGenerally slower
Memory efficiencyLess memory efficientMore memory efficient

The best choice for you will depend on your specific needs. If you need a collection that can be accessed by multiple threads at the same time, then you should use a hashtable. If you do not need synchronization, then you can use a hashmap, which will be faster and less memory-intensive.

Here are some additional things to keep in mind when choosing between a hashmap and a hashtable:

  • If you are using a hashmap in a multithreaded application, you should be careful to avoid race conditions. This can be done by using the lock keyword to synchronize access to the hashmap.
  • If you are storing large objects in a hashmap, you should be aware that the hashmap will need to allocate memory for each object. This can lead to memory fragmentation, which can affect performance.
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