如何在Java中保存和加载对象？我试过了，但它一直抛出IOexception

我不知道为什么IOException会被抓到。因为我已经创建了该文件并通过ObjectOutputStream运行它。例外消息是：

java.io.NotSerializableException:cafesys.Order

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可能是因为文件很糟糕？它说：文件糟糕的写入被中止；java.io.NotSerializableException:cafesys.Order。它的意思是：第一，你的文件很烂，第二，cafesys.Order是不可序列化的。找到咖啡馆。订购并使其可连载。哈哈@CocoNess真的很有趣。。。

public class DriverClass implements Serializable {
    CafeManager cafe = new CafeManager(); - Creates the object 

    public static void main(String args[]) throws FileNotFoundException, IOException, ClassNotFoundException{
        CafeManager newcafe;

        newcafe = load(); - Calls the load module

        SystemMenu menu = new SystemMenu();
        menu.displaymenu(); - Running of the menu


        newcafe = new CafeManager(newcafe.getMenuItems(),newcafe.getOrders()); - Once the user exits the menu, file should be saved


        save(newcafe);

    }

    public static void save(CafeManager newcafe) throws FileNotFoundException, IOException{
        try{
            FileOutputStream fileOut = new FileOutputStream("system.dat");

            ObjectOutputStream out = new ObjectOutputStream(fileOut);

            out.writeObject(newcafe);
        }
        catch (FileNotFoundException fe){
            System.out.println("File Not found.");
        }
        catch (IOException ie){
            System.out.println("File Crappy" + ie.getMessage()); //Output: File Crappycafesys.Order
        }

    }

    public static CafeManager load() throws FileNotFoundException, IOException, ClassNotFoundException{
        CafeManager curcafe = new CafeManager();
        FileInputStream fileIn = new FileInputStream("system.dat");

        ObjectInputStream in = new ObjectInputStream(fileIn);

        try{
            curcafe = (CafeManager) in.readObject();
        }
        catch(ClassCastException | ClassNotFoundException ce){
            //
        }
        catch (FileNotFoundException fe){
            System.out.println("File Not found.");
        }
        catch (IOException ie){
            System.out.println("File Crappy" + ie.getMessage()); //Output: File Crappy writing aborted; java.io.NotSerializableException: cafesys.Order
        }

        return curcafe;
    }