Get organisation users userNames in combobox

I want to get all my users Usernames in a combobox , i wrote the follow code :

import org.bonitasoft.engine.identity.UserCriterion; import org.bonitasoft.engine.identity.User;

int nb = apiAccessor.getIdentityAPI().getNumberOfUsers();
ArrayList listUsersSe = apiAccessor.identityAPI.getUsers(0, nb, UserCriterion.USER_NAME_ASC);
ArrayList listMailSe = new ArrayList();

for (User uSe : listUsersSe) {
String eMailSe = BonitaUsers.getUser(apiAccessor, uSe.getId()).getUserName();
listMailSe.add(eMailSe);
}
return listMailSe;

But my list is empty ?

Strange because it works for me:

import org.bonitasoft.engine.identity.UserCriterion;
import org.bonitasoft.engine.identity.User;

int nb = apiAccessor.getIdentityAPI().getNumberOfUsers();
ArrayList listUsersSe = apiAccessor.identityAPI.getUsers(0, nb, UserCriterion.USER_NAME_ASC);
ArrayList listUsers = new ArrayList();

for (User uSe : listUsersSe) {
String eUSe = BonitaUsers.getUser(apiAccessor, uSe.getId()).getUserName();
listUsers.add(eUSe);
}
return listUsers;