Java 创建add（）方法将对象插入数组中，得到的都是空值

这是一个名为Doglist的类，用于将对象添加到数组中

public class DogList {
  private int numItems;
  private DogItem[] dogListArray;
  private int position;

  DogList ()    {
    numItems=0;
    position = 0;
    dogListArray = new DogItem[10]; 
}

public void add (DogItem item)  {
    dogListArray[numItems++]= new DogItem(item.getName(), 
                                          item.getBreed(),
                                          item.getWeight(),
                                          item.getOwner1(),
                                          item.getOwner2()
                                          );
   }

public String toString()    {
    String result = "";
    for (int i=0; i<numItems; i++)  {
        result += dogListArray[i].toString() + "\n";
    }
    return result;
}
  public DogItem searchForDogItem (DogItem gi)  {

    System.out.println("Here is your obj value: " + gi ); 

    return null;
}//This is the one im having trouble with.
}

我走的时候会设法把事情弄清楚

这是我得到的输出

---

这是您的obj值：null null 0.0 null null

好，下面是它可能的外观。就因为我已经看错了。但是，您可能希望重写DogItem的toString（）方法

这方面的主要方法示例：

public class Main {

    public static void main(String[] args) {
        DogItem dogItem = new DogItem("Spot", "Dalmation", "45", "Bob", "Sandy");
        DogItem.add(dogItem);

        DogItem result = DogItem.searchForItem("Spot");

        if (result == null) {
            System.out.println("Dog not found");
            // GUI error output goes here
        } else {
            System.out.println("Here is your obj value: " + result);
            // Where your GUI stuff goes
        }
    }
}

public class DogItem {
    private static DogItem[] dogListArray = new DogItem[100];
    private static int numItems = 0;

    private String name;
    private String breed;
    private String weight;
    private String owner1;
    private String owner2;

    public DogItem(String name, String breed, String weight, String owner1, String owner2) {
        this.name = name;
        this.breed = breed;
        this.weight = weight;
        this.owner1 = owner1;
        this.owner2 = owner2;
    }

    public static void add(DogItem dogItem) {
        dogListArray[numItems++] = dogItem;
    }

    public static DogItem searchForItem(String name) {
        DogItem dogItem = null;
        for (DogItem result : dogListArray) {
            if (result != null) {
                if (result.getName() == name) {
                    dogItem = result;
                }
            }
        }
        return dogItem;
    }

    @Override
    public String toString() {
        String result = name + ", " + breed + ", " + weight + ", " + owner1 + " " + owner2;
        return result;
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getBreed() {
        return breed;
    }
    public void setBreed(String breed) {
        this.breed = breed;
    }
    public String getWeight() {
        return weight;
    }
    public void setWeight(String weight) {
        this.weight = weight;
    }
    public String getOwner1() {
        return owner1;
    }
    public void setOwner1(String owner1) {
        this.owner1 = owner1;
    }
    public String getOwner2() {
        return owner2;
    }
    public void setOwner2(String owner2) {
        this.owner2 = owner2;
    }
}

例如：

public class Main {

    public static void main(String[] args) {
        DogItem dogItem = new DogItem("Spot", "Dalmation", "45", "Bob", "Sandy");
        DogItem.add(dogItem);

        DogItem result = DogItem.searchForItem("Spot");

        if (result == null) {
            System.out.println("Dog not found");
            // GUI error output goes here
        } else {
            System.out.println("Here is your obj value: " + result);
            // Where your GUI stuff goes
        }
    }
}

public class DogItem {
    private static DogItem[] dogListArray = new DogItem[100];
    private static int numItems = 0;

    private String name;
    private String breed;
    private String weight;
    private String owner1;
    private String owner2;

    public DogItem(String name, String breed, String weight, String owner1, String owner2) {
        this.name = name;
        this.breed = breed;
        this.weight = weight;
        this.owner1 = owner1;
        this.owner2 = owner2;
    }

    public static void add(DogItem dogItem) {
        dogListArray[numItems++] = dogItem;
    }

    public static DogItem searchForItem(String name) {
        DogItem dogItem = null;
        for (DogItem result : dogListArray) {
            if (result != null) {
                if (result.getName() == name) {
                    dogItem = result;
                }
            }
        }
        return dogItem;
    }

    @Override
    public String toString() {
        String result = name + ", " + breed + ", " + weight + ", " + owner1 + " " + owner2;
        return result;
    }

    public String getName() {
        return name;
    }
    public void setName(String name) {
        this.name = name;
    }
    public String getBreed() {
        return breed;
    }
    public void setBreed(String breed) {
        this.breed = breed;
    }
    public String getWeight() {
        return weight;
    }
    public void setWeight(String weight) {
        this.weight = weight;
    }
    public String getOwner1() {
        return owner1;
    }
    public void setOwner1(String owner1) {
        this.owner1 = owner1;
    }
    public String getOwner2() {
        return owner2;
    }
    public void setOwner2(String owner2) {
        this.owner2 = owner2;
    }
}

不过，我建议您做以下更改：

    private static ArrayList<String> owners;
    private static ArrayList<DogItem> dogsList;
    public DogItem(String name, String breed, String weight, String owner) {
        this.name = name;
        this.breed = breed;
        this.weight = weight;
        this.owners.add(owner);
    }
    public void init() {
        owners = new ArrayList<String>();
        dogsList = new ArrayList<DogItem>();
    }
    public void addDog(DogItem dogItem) {
        dogsList.add(dogItem);
    }
    public DogItem searchForItem(String name) {
        DogItem dogItem = null;
        for (DogItem result : dogsList) {
            if (result != null) {
                if (result.getName() == name) {
                    dogItem = result;
                }
            }
        }
        return dogItem;
    }
    public void addOwner(String owner) {
        owners.add(owner);
    }
    public String getOwner() {
        return owners.get(owners.size() - 1);
    }

私有静态数组列表所有者；
私有静态数组列表；
公共狗项（字符串名称、字符串品种、字符串重量、字符串所有者）{
this.name=名称；
这个品种；
重量=重量；
this.owner.add（owner）；
}
公共void init（）{
所有者=新的ArrayList（）；
dogsList=newarraylist（）；
}
公共无效添加狗（DogItem DogItem）{
添加（dogItem）；
}
public DogItem searchForItem（字符串名称）{
DogItem DogItem=null；
用于（DogItem结果：dogsList）{
如果（结果！=null）{
if（result.getName（）==name）{
dogItem=结果；
}
}
}
退货项目；
}
公共void addOwner（字符串所有者）{
所有者。添加（所有者）；
}
公共字符串getOwner（）{
返回owners.get（owners.size（）-1）；
}

您遗漏了很多代码。请创建一个。我正要说同样的话。。。你对变量或对象的引用我们看不到你在做什么。。。我有一个线索，但是你没有足够的信息来说明问题所在。现在更新我在下面贴了一个答案，我已经尝试过了。谢谢你，我现在正在查看。在那里添加了错误检查，以防找不到狗。另外请注意，else语句是您将值分配给正在实现的GUI的地方。好的，我明白了，您的代码可以工作，但我现在的问题是，您是否可以在哪里打印“字符串名称”在searchForItem方法中，不进行检查，它会为所有值打印null，甚至更好，它会打印出对象位置..我意识到了你在说什么，并修复了这个问题。这或多或少就是你要找的。是的，这几乎是一针见血。我知道应该使用数组列表，但我想使用数组来确保更好地理解它。数组的类型并将对象传递给它们。谢谢你的帮助和洞察力。