Combbox list is not being loaded

<zscript>
  public void loadContacts() {
      ListModelList contactsModel= new ListModelList( dbc.getAllContacts(contacts) );
      System.out.println(contacts.isEmpty());
      to.setModel(contactsModel);
     }
</zscript>

each="@{contacts.com_receivers}">

<?init class="org.zkoss.zkplus.databind.AnnotateDataBinderInit" ?>

<zk><zscript>
	public class Person {
		private String firstName;
		private String lastName;

		public Person(String a, String b) {
			this.firstName = a;
			this.lastName = b;
		}
		public void setFirstName(String firstname) {
			this.firstName = firstname;
		}
		public void setLastName(String lastname) {
			this.lastName = lastname;
		}
		public String getLastName() {
			return this.lastName;
		}
		public String getFirstName() {
			return this.firstName;
		}
	}
	
	public class Test{
		List list;
	
		public Test(){
		list = new ArrayList();
		list.add(new Person("yy", "xx"));
		list.add(new Person("yy", "xx"));
		list.add(new Person("yy", "xx"));
		list.add(new Person("yy", "xx"));
		}
		
		public List getPersons(){
			return list;
		}
	}
	
	
	Test test = new Test();
</zscript>
	<listbox id="lb" model="@{test.persons}">
		<listhead>
			<listheader>A</listheader>
			<listheader>B</listheader>
		</listhead>
			<listitem self="@{each='person'}" value="@{person}">
				<listcell label="@{person.firstName}" />
				<listcell label="@{person.lastName}" />
			</listitem>
	</listbox>
</zk>