Java引用類

Question

我有以下兩類動物和動物園，

動物類

public class Animal {
    private int id;
    private String name;
    private String  animal_order;
    private String family;
    private String  genus;
    private String  species;
    private int number_avilable;
    private Zoo _zoo;

    public Animal() {

    }

    public Animal(ArrayList<Animal> allAnimals) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    public Animal (int id, String name, String  animal_order, String family, String  genus, String  species,int number_avilable, Zoo _zoo){
        this.id = id;
        this.name = name;
        this.animal_order = animal_order;
        this.family = family;
        this.genus = genus;
        this.species = species;
        //this.zoo = zoo;
        this.number_avilable = number_avilable;
        this._zoo = _zoo;

    }
}

動物園班

public class Zoo {
    private String zoo_name;
    private String  link;
    private String lat;
    private String  lng;
    private String  postcode;
    private String image;

    public Zoo() {

    }

    public Zoo(ArrayList<Zoo> allZoos) {
        throw new UnsupportedOperationException("Not supported yet."); //To change body of generated methods, choose Tools | Templates.
    }

    public Zoo (String zoo_name, String  link,String  postcode, String image){
        this.zoo_name = zoo_name;
        this.link = link;
        //this.lat = lat;
        //this.lng = lng;
        this.postcode = postcode;
        this.image = image;
    }
}

正如您從我的代碼中看到的那樣，我嘗試在Animal中引用Zoo類。 我在Animal類中有以下方法，

public static ArrayList<Animal> getAllAnimals() throws Exception {
    PreparedStatement query = null;
    Connection conn = null;

    ArrayList<Animal> results = new ArrayList();
    try {

        // connect to database
        conn = Database.mySqlDBConn().getConnection();
        // run a query
        query = conn.prepareStatement("{CALL get_animal()}");
        ResultSet rs = query.executeQuery();
        while (rs.next())
        {
            int id = rs.getInt("id");
            String name = rs.getString("name");
            String  animal_order = rs.getString("animal_order");
            String family = rs.getString("family");
            String  genus = rs.getString("genus");
            String  species = rs.getString("species");
            int number_avilable= rs.getInt("number_avilable");
            String zoo_name = rs.getString("zoo_name");
            String link = rs.getString("link");
            String postcode = rs.getString("postcode");
            String image = rs.getString("image");
            Zoo _zoo = new Zoo(zoo_name, link, postcode, image);
            Animal animal = new Animal(id, name,animal_order,family, genus, species,number_avilable, _zoo);
            results.add(animal);
        }
    }
}

上面的方法應該返回一個既包含動物又包含動物園的數組列表，但此刻它僅返回動物而不是動物園信息。 我一直在通過堆棧溢出來獲取類參考和內容，但無法找出線索。

僅供參考，我的存儲過程工作正常。

Answer 1

您想要同時包含動物和動物園的ArrayList嗎？ 看起來您只是將動物添加到了數組列表中，並且將動物園添加到了動物中，因此，如果要獲取動物園，只需在Animal類中添加一個吸氣劑即可：

public Zoo getZoo() {
    return _zoo;
}