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How to convert a Java list to a set?
A list can be converted to a set object using Set constructor. The resultant set will elliminate any duplicate entry present in the list and will contains only the unique values.
Set<String> set = new HashSet<>(list);
Or we can use set.addAll() method to add all the elements of the list to the set.
set.addAll(list);
Using streams as well, we can get a set from a list.
set = list.stream().collect(Collectors.toSet());
Example
Following is the example showing the list to set conversion via multiple ways −
package com.tutorialspoint;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
import java.util.stream.Collectors;
public class CollectionsDemo {
public static void main(String[] args) {
List<Integer> list = new ArrayList<>(Arrays.asList(1,2,3,3,3,4,5));
System.out.println("List: " + list);
Set<Integer> set = new HashSet<>(list);
System.out.println("Set: " + set);
set = new HashSet<>();
set.addAll(list);
System.out.println("Set: " + set);
set = new HashSet<>();
set = list.stream().collect(Collectors.toSet());
System.out.println("Set: " + set);
}
}Output
This will produce the following result −
List: [1, 2, 3, 3, 3, 4, 5] Set: [1, 2, 3, 4, 5] Set: [1, 2, 3, 4, 5] Set: [1, 2, 3, 4, 5]
Updated on: 09-May-2022
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