Test the same object add to set

test_set.java

public static void main(String[] args) {

    SomeClass1 a1 = new SomeClass1();
    a1.setName("A");
    SomeClass1 a2 = new SomeClass1();
    a2.setName("A");
    SomeClass1 b = new SomeClass1();
    b.setName("B");
    SomeClass1 c = new SomeClass1();
    c.setName("C");

    Map<String, SomeClass1> map = new HashMap<>();
    map.put(a1.getName(), a1);
    map.put(a2.getName(), a2);
    map.put(b.getName(), b);
    map.put(c.getName(), c);

    List<String> stringList = Arrays.asList("A", "A", "B", "A", "B", "C", "B", "C", "A", "B");

    final Map<String, Set<SomeClass1>> collect = stringList.stream()
            .collect(
                    groupingBy(
                            Function.identity(),
                            mapping(
                                    map::get,
                                    toSet()
                            )
                    )
            );

    System.out.println(collect);
    System.out.println(collect.get("A").getClass());
}