What are the differences between Hashmap and Hashtable?

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What are the differences between HashMap and Hashtable in Java?

Which is more efficient?

java hashmap collection

  • Summarizing in a row: The Hashtable is synchronized (thread-safe). The Hashmap, no.

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    Consequently, if it is a situation without competition, in which either use one or the other, the non-synchronized version (Hashmap) will be more efficient.

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Hashmap

  • Is not synchronized
  • Accepts null values and a null key
  • It is possible to scan the entire structure with a simple iterator
  • Has containsValue() and containsKey()
  • Is faster
  • Consumes less memory
  • More modern
  • Mother: AbstractMap

Hashtable

  • Synchronized and can be easily used in concurrent environment
  • Does not accept null
  • Iterating is more complicated
  • Has contains()
  • Has overhead by synchronization
  • Takes up more memory
  • Considered obsolete
  • Mother: Dictionary

I withdrew the information mainly of that response in the OS.

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