java - 无法从文件中读取对象并将它们放入java中的链表中

Question

我想从文件中读取对象并将数据放入LinkedList并返回对其的引用。但是当我尝试这个方法时，它返回没有数据的 LinkedList。

private static LinkedList<Course> readFromFile(String fileName)
        throws FileNotFoundException, IOException {
    LinkedList<Course> tmp = new LinkedList<Course>();

    reader = new ObjectInputStream(new FileInputStream(fileName));

    try {
        LinkedList<Course> readObject2 = (LinkedList<Course>) reader
                .readObject();
        LinkedList<Course> readObject = readObject2;
        tmp = readObject;
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }

    return tmp;
}

我的写作方法是这样的

private static boolean writeToFile(String fileName, LinkedList<Course> templist)
        throws IOException {
    LinkedList<Course> templist1 = new LinkedList<Course>();

    if (createFile(fileName)) {
        FileOutputStream outF = new FileOutputStream(fileName);

        outO = new ObjectOutputStream(outF);
        outO.writeObject(templist1);

        //outO.flush();
        return true;
    }
    else
        return false;
}

<小时/>

写法是这样的

private static boolean writeToFile(String fileName, LinkedList<Course> templist) throws IOException {
    LinkedList<Course> templist1 = new LinkedList<Course>();

    if (createFile(fileName)) {
        FileOutputStream outF = new FileOutputStream(fileName);

        outO = new ObjectOutputStream(outF);
        outO.writeObject(templist1);

        //outO.flush();
        return true;
    }
    else
        return false;
}

Answer 1

类(class)类正在实现 java.io.Serializable ？
当您使用 ObjectInputStream 从文件中读取对象时，其顺序应与之前使用 ObjectOutputStream 存储的顺序相同。并且具有相同的对象类型。

如果您尝试阅读:

 (LinkedList<Course>) reader.readObject();

您必须将其存储为:

ObjectOutputStream writer = new ObjectOutputStream(
        new FileOutputStream(fileName));

writer.writeObject(yourLinkedListToSave);

正如您的代码所示:

private static boolean writeToFile(String fileName, LinkedList<Course> templist) throws IOException {
    // Dont forget to initialize with your list else the list still empty
    LinkedList<Course> templist1 = new LinkedList<Course>(templist);

    if (createFile(fileName)) {
        FileOutputStream outF = new FileOutputStream(fileName);

        outO = new ObjectOutputStream(outF);
        outO.writeObject(templist1);

        //outO.flush();
        return true;
    }
    else
        return false;
}