java - 从文件读取对象的 ArrayList 时出错？

Question

我有一个对象数组存储在“rootFile”中。我想将对象读回到另一个 ArrayList 中。到目前为止我尝试过这个:

List<NoteCard> cardArray = new ArrayList<>();

try {
    FileInputStream fis = openFileInput(rootFile);
    ObjectInputStream ois = new ObjectInputStream(fis);
    cardArray = (List<NoteCard>)ois.readObject();
    ois.close();
    fis.close();
} catch(FileNotFoundException e) {
    e.printStackTrace();
} catch(IOException e) {
    e.printStackTrace();
} catch(ClassNotFoundException e) {
    e.printStackTrace();
}

Answer 1

您可以通过执行以下操作删除未经检查的强制转换:

ArrayList<NoteCard> cardArray = new ArrayList<>();

try {
    FileInputStream fis = openFileInput(rootFile);
    ObjectInputStream ois = new ObjectInputStream(fis);
    Object object = ois.readObject();
    if (object instanceof ArrayList) {
        ArrayList arrayList = (ArrayList) object;
        for (Object object : arrayList) {
            cardArray.add((NoteCard) object);
        }
    }
    ois.close();
    fis.close();
} catch(FileNotFoundException e) {
    e.printStackTrace();
} catch(IOException e) {
    e.printStackTrace();
} catch(ClassNotFoundException e) {
    e.printStackTrace();
}