java remove duplicates from list by property
import static java.util.Comparator.comparingInt;
import static java.util.stream.Collectors.collectingAndThen;
import static java.util.stream.Collectors.toCollection;
...
List<Employee> unique = employee.stream()
.collect(collectingAndThen(toCollection(() -> new TreeSet<>(comparingInt(Employee::getId))),
ArrayList::new));