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what is the difference between hashset and hashmap in java?


HashSet extends AbstractSet and implements the Set interface. It not maintains any order for its elements. It uses hash table for storage.



HashMap extends AbstractMap class and implements the Map interface. It contains the elements in key-value pair form. It not maintains any order for its elements. It not allowed duplicate key. A HashMap can have only one null key and multiple null values.


HashSet contains only values whereas HashMap contains entry(key,value). HashSet can be iterated but HashMap need to convert into Set to be iterated.

Java interview questions on collections

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