Java Data StructuresLesson 66Free preview

Java HashSet

This lesson is part of Java · All levels

Summary

HashSet is the most popular set implementation that stores unique elements using hashing mechanisms on the internal HashMap. The add, remove, and contain operations run on average, making them very fast for big data. But remember, the order of the elements when iterated is unreliable.

Key points

No order guarantees; iterations can change when the contents of the set change
Uniqueness depends heavily on the correct spelling of hashCode() and equals()
16 built-in capacity with load factor 0.75 as the magnification threshold
Allowing exactly one element
Elements whose hash changes after entering the set can appear to be missing from the set

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