[英]Java: XMLEncoder writeObject child object
I'm doing a little homework on Java, but I'm not good at it and I'm having issues trying to use XMLEncoder to store an App objects to a file. 我正在Java上做一些功课,但我不擅长此事,并且在尝试使用XMLEncoder将App对象存储到文件时遇到问题。
In short my App has and abstract class called animal
and another ones that extend the previous one called dog
and cat
. 简而言之,我的App有一个抽象类叫做
animal
,另一个扩展了前一个类的dog
和cat
。 In my main App I've a static method to create new animals that adds the new animal object to a static ArrayList of type animal
: public static ArrayList<animal> animalArray = new ArrayList<animal>();
在我的主要应用我有一个静态方法来创建新的动物,其将所述新的动物对象类型的静态的ArrayList
animal
: public static ArrayList<animal> animalArray = new ArrayList<animal>();
Creating an animal at kingdom.java: 在Kingdom.java中创建动物:
private static void newAnimal(ArrayList<animal> animalArray) {
System.out.print(" Enter a name for the dog > ");
animalArray.add(new dog(keyboard.nextLine()));
System.out.println(" New dog with name " + animalArray.get(animalArray.size()-1).getName() + ".\n");
try {
FileOutputStream afos = new FileOutputStream("animals.xml");
XMLEncoder encoder = new XMLEncoder(afos);
encoder.writeObject(animalArray.get(animalArray.size()-1));
encoder.close();
} catch(IOException ioe){
System.out.print("[ERROR!]");
}
}
My abstract animal class: animal.java: 我的抽象动物类: animal.java:
public abstract class animal {
private static int alloc = 0;
protected int id;
private String name;
animal() {
alloc++;
id = alloc;
}
public void play() {
System.out.print(" The animal (" + this.id + ") " + this.name + " is now playing... ");
}
public void setName(String lname) {
this.name = lname;
}
public String getName() {
return this.name;
}
public static int countAnimals() {
return alloc;
}
}
Now, my dog class: dog.java: 现在,我的狗类: dog.java:
public class dog extends animal {
dog(String theName) {
this.setName(theName);
}
@Override
public void play() {
super.play();
System.out.println(" Dog Stuff!");
}
}
When I try to run the code I get: 当我尝试运行代码时,我得到:
java.lang.InstantiationException: dog
Continuing ...
java.lang.Exception: XMLEncoder: discarding statement XMLEncoder.writeObject(dog);
Continuing ...
What am I missing? 我想念什么? Thank you ;)
谢谢 ;)
You should use as following: 您应该使用以下方法:
encoder.writeObject(animalArray.get(animalArray.size()-1).getName()); encoder.writeObject(animalArray.get(animalArray.size()-1).getName());
The Dog object itself can't be saved into XMLEncoder. Dog对象本身无法保存到XMLEncoder中。
Thx. 谢谢。
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