What is a HashSet?
Part of the Logic & Flow section of Coddy's Java journey — lesson 22 of 59.
A HashSet is a data structure that stores a collection of unique elements. It works like a set in mathematics, where every item can appear only once.
Think of it like a basket that holds individual fruits—if you try to put the same fruit in twice, it will only keep one copy.
To use a HashSet in Java, you need to import it at the beginning of your code:
import java.util.HashSet;Cheat sheet
A HashSet is a data structure that stores a collection of unique elements, where every item can appear only once.
To use a HashSet in Java, import it:
import java.util.HashSet;Try it yourself
This lesson doesn't include a code challenge.
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Logic & Flow
1Multi-dimensional Arrays
2D Arrays BasicsAccessing 2D Array ElementsNested Loops with 2D ArraysRecap - 2D ArraysMatrix Addition & SubstractionJagged Arrays3D Arrays And BeyondCommon 2D Array PatternsRecap - All About Arrays4HashSet Part 1
What is a HashSet?Adding an ElementRemoving an ElementChecking if an Element ExistsEmpty and SizeClear and CloneRecap - HashSet2HashMap Part 1
What is a HashMap?Declare a HashMapAccessing ValuesCheck If Key ExistsModifying DictionariesRecap - HashMap