public void departmentChangeListener(ValueChangeEvent event){

    Long id = (Long) event.getNewValue();

    department = id;

    if(department == -1 || department == 0){
        employee=0;
        displayEmployee = false;

    } else{

        changeEmployee();
        employee=0;
        displayEmployee = true;
    }
}

This is the method that call in valuechangeListener attribute of ice:selectOneMenu tag but here problem is value of employee set 0 when we second time change value from selectOneMenu's List.