Java Convert ArrayList to HashSet

Tags: ArrayList HashSet

In this Java core tutorial we learn how to convert a java.util.ArrayList to a java.util.HashSet in Java programming language.

How to convert ArrayList to HashSet in Java

In Java, with a given ArrayList object we can use the HashSet(Collection<? extends E> c) constructor to create a new HashSet object from the ArrayList elements.

In the following Java program we show how to use this HashSet constructor to convert an ArrayList object to a HashSet object.

ConvertArrayListToSetExample1.java 

import java.util.ArrayList;
import java.util.HashSet;
import java.util.List;
import java.util.Set;

public class ConvertArrayListToSetExample1 {
    public static void main(String... args) {
        List<String> arrayList = new ArrayList<>();

        arrayList.add("Java");
        arrayList.add("Kotlin");
        arrayList.add("Groovy");

        Set<String> hashSet = new HashSet<>(arrayList);

        System.out.println("ArrayList: " + arrayList);
        System.out.println("HashSet: " + hashSet);
    }
}
The output as below. 
ArrayList: [Java, Kotlin, Groovy]
HashSet: [Java, Groovy, Kotlin]

Happy Coding 😊

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