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Can we convert a List to Set and back in Java?
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);
On similar pattern, we can get a list from a set using its constructor.
List<Integer> list = new ArrayList<Integer>(set);
Example
Following is the example showing the conversion of list to set and set to list −
package com.tutorialspoint;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashSet;
import java.util.List;
import java.util.Set;
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);
List<Integer> list1 = new ArrayList<Integer>(set);
System.out.println("List: " + list1);
}
}Output
This will produce the following result −
List: [1, 2, 3, 3, 3, 4, 5] Set: [1, 2, 3, 4, 5] List: [1, 2, 3, 4, 5]
Updated on: 09-May-2022
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