import java.util.*;
import java.util.stream.*;

var first = new HashSet<Integer>(
    Arrays.asList(1, 2));
var second = new HashSet<Integer>(
    Arrays.asList(1, 2));
var third = new HashSet<Integer>(
    Arrays.asList(1, 2, 3));

var isEqual = first.equals(second);
//isEqual is true

var isIntersects = first.stream()
    .filter(i -> third.contains(i)).count() > 0;
//isIntersects is true

var isThirdSubset = first.containsAll(third);
//isSubset is false

System.out.println("isEqual is " + isEqual);
System.out.println("isIntersects is " + isIntersects);
System.out.println("isThirdSubset is " + isThirdSubset);