Get the intersection of two sets in Java

To get the intersection of two sets, use the retainAll() method. Here are out two set −

First set −

HashSet <String> set1 = new HashSet <String>(); set1.add("Mat"); set1.add("Sat"); set1.add("Cat");

Second set −

HashSet <String> set2 = new HashSet <String>(); set2.add("Mat"); set2.add("Cat"); set2.add("Fat"); set2.add("Hat");

Get the intersection −

set1.retainAll(set2);

The following is an example to get the intersection of two sets −

Example

 Live Demo

import java.util.*; public class Demo {    public static void main(String args[]) {       HashSet <String> set1 = new HashSet <String>();       HashSet <String> set2 = new HashSet <String>();       set1.add("Mat");       set1.add("Sat");       set1.add("Cat");       System.out.println("Set1 = "+ set1);       set2.add("Mat");       set2.add("Cat");       set2.add("Fat");       set2.add("Hat");       System.out.println("Set2 = "+ set2);       set1.retainAll(set2);       System.out.println("Intersection = "+ set1);    } }

Output

Set1 = [Mat, Sat, Cat] Set2 = [Mat, Cat, Fat, Hat] Intersection = [Mat, Cat]