EN
Java - retain from HashSet (retainAll())
0 points
In this article, we would like to show you how to retain from HashSet all of its elements that are contained in the specified collection in Java.
Quick solution:
xxxxxxxxxx1
myHashSet1.retainAll(myHashSet2);
In this example, we have two HashSets: letters1 and letters2. Using retainAll() method we remove elements from letters1 and retain only elements contained in letters2.
xxxxxxxxxx1
import java.util.*;2
3
public class Example {4
5
public static void main(String[] args) throws NullPointerException {6
Set<String> letters1 = new HashSet<>();7
letters1.add("A");8
letters1.add("B");9
letters1.add("C");10
letters1.add("D");11
letters1.add("E");12
13
14
System.out.println("Before retainAll(): " + letters1);15
16
Set<String> letters2 = new HashSet<>();17
letters2.add("A");18
letters2.add("B");19
letters2.add("C");20
21
letters1.retainAll(letters2); // retain elements from letters222
23
System.out.println("After retainAll(): " + letters1);24
}25
}Output:
xxxxxxxxxx1
Before retainAll(): [A, B, C, D, E]2
After retainAll(): [A, B, C]