Don't copy this implementation please :P

EmployeeServiceSingleton

public class EmployeeServiceSingleton {

  private static final EmployeeServiceSingleton instance = new EmployeeServiceSingleton();

  private final EmployeeDao employeeDao;

  private EmployeeServiceSingleton() {
    employeeDao = ServiceLocator.getEmployeeDao();
  }

  public static EmployeeServiceSingleton getInstance() {
    return instance;
  }

  public String findManagerName(final Long employeeId) {
    if (null == employeeId) {
      throw new IllegalArgumentException("employeeId must not be null");
    }

    return employeeDao.findManager(employeeId).getName();
  }
}