Question

我正在尝试创建一种在Java中保存/加载对象的方法，我有类Item：

public class Item implements Serializable{
//Variables
private String name, desc;
private int price;

//Constructors
public Item(){
    this.name=this.desc="NA";
}
public Item(String name,String desc,int price){
    this.name=name;
    this.desc=desc;
    this.price=price;
}
public Item(String name){
    load(name);
}
public Item(Item i){
    this.name=i.name;
    this.desc=i.desc;
    this.price=i.price;
}

//Getters and Setters
public void setName(String name) {
    this.name = name;
}
public void setPrice(int price) {
    this.price = price;
}
public void setDesc(String desc) {
    this.desc = desc;
}
public String getName() {
    return name;
}
public String getDesc() {
    return desc;
}
public int getPrice() {
    return price;
}

public void save(){
    try{
        String path = System.getProperty("user.home") + "/JavaGame/Item/";
        new File(path).mkdirs();
        path+=this.name;
        path+=".dat";
        ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream(path));
        outputStream.writeObject(this);
        outputStream.flush();
        outputStream.close();
    }
    catch(Exception e){
        System.out.println("Error saving: "+e.getMessage());
    }
}
public void load(String name){
    try {
        String path = System.getProperty("user.home") + "/JavaGame/Item/";
        path+=name;
        path+=".dat";
        ObjectInputStream in = new ObjectInputStream(new FileInputStream(path));
        Item i = (Item) in.readObject();
        this.name=name;
        this.desc=i.desc;
        this.price=i.price;
        in.close();
    }
    catch(Exception e){
        System.out.println("Error loading: "+e.getMessage());
    }
}

public boolean equals(Object o){
    if(o==null||o.getClass()!=this.getClass())return false;
    Item i = (Item) o;
    return i.name.equals(this.name);
}
public String toString(){
    return new StringBuilder().append(this.name).append("\n").append(this.desc).toString();
}
public Item clone(){
    return new Item(this);
}

}

我想创建项目类型，例如可用和装甲（例如）。所以我将创建一个名为ArmorPiece的新类，它只有一个防御属性。我们假设代码是：

public class ArmorPiece extends Item{
    private int defense;

    public ArmrPiece(String name, int defense){
        setName(name);
        this.defense = defense;
    }

    public String toString(){
        return "It's an armor piece";
    }
}

在这个项目中，我将所有项目信息保存在文件夹/ JavaGame / Item /中，并且我想将所有项目保存在同一文件夹中，当我运行如下所示的测试时，它进入了else括号，你知道吗？使“物品”变成“ArmorPiece”？

public static void main(String args[]){
    new ArmorPiece("boots",10).save();
    Item m = new Item("boots");//It will load the boots info into an Item
    if(m.getClass().getName().equals("ArmorPiece")){//It should enter the if since it is an ArmorPiece
        ArmorPiece ap=(ArmorPiece) m;
        System.out.println(ap);
    }
    else{//Enters this brackets, but it shouldn't
        System.out.println(m);
    }
}

Answer 1

这是因为你创建了Item类。您无法在创建后更改对象类。我建议您将load方法设为静态并从中返回i。

Answer 2

它可能是有用的，但我认为你应该使用一种方法一次加载所有内容（例如在HashMap中），然后在那里查找它，你甚至可以在打开程序时加载Map。例如：

public class AllItems{
    Map<String,Item> allItems;

    public AllItems(){
        allItems = new HashMap<String,Item>();
        //Load all items here(You can save them all in one file)
    }

    public Item getItem(String name){
        return allItems.get(name);//You need to make this always work, so you should check if the item exists first.
    }
}

这只是一个例子，但您可以尝试这样做。

在java中保存和加载子类

2 个答案: