public class DepartmentLaboratoryService {
		
    private List<DepartmentLaboratory> departmentList;

	public int getChildCount(DepartmentLaboratory parent, int limit, int offset) {
    	Stream<DepartmentLaboratory> stream = getChildren(parent).stream();

        return stream.collect(Collectors.toList()).size();
	}
    
    public Boolean hasChildren(DepartmentLaboratory parent) {

        return departmentList.stream()
                .anyMatch(department -> Objects.equals(parent, department.getParent()));
    }

    public Collection<DepartmentLaboratory> fetchChildren(DepartmentLaboratory parent, int limit, int offset,
			 List<DepartmentLaboratorySort> sortOrders) {
		
    	// get filtered list
    	Stream<DepartmentLaboratory> stream = getChildren(parent).stream();
    	
		// apply sorting
		Comparator<DepartmentLaboratory> comparator = (o1, o2) -> 0;
		for (DepartmentLaboratorySort departmentSort : sortOrders) {
			switch (departmentSort.getPropertyName()) {
				case DepartmentLaboratorySort.NAME:
					comparator = comparator.thenComparing(DepartmentLaboratory::getPatientName);
					break;
			}
			if (!departmentSort.isDescending()) comparator = comparator.reversed();
		}

		stream = stream.sorted(comparator);
				
		// return results
    	return stream.skip(offset).limit(limit).collect(Collectors.toList());
	}
    
    private List<DepartmentLaboratory> getChildren(DepartmentLaboratory parent){
        return departmentList.stream()
                .filter(department -> Objects.equals(parent, department.getParent())).collect(Collectors.toList());
    }

	//my code
	public List<DepartmentLaboratory> getDepartmentList() {
		return departmentList;
	}

	public void setDepartmentList(List<DepartmentLaboratory> departmentList) {
		this.departmentList = departmentList;
	}
}