序列化包含对象ArrayList的对象

Question

public class User  implements  Serializable{

    public String name;
    public String surname;
    public List<Picked> pickedBooks = new ArrayList<>();

    // Code omitted.
}

然后去上课:

public class Picked {

    public Book book;
    public int period;
    public int cost;

    // Code omitted.
}

和班级书:

public class Book {

    public String name;
    public String bookTitle;
    public int howMany;

    // Code omitted.
}

所以在主要的我创建新用户并序列化它:

User user = new User();
user.setName("John");
user.setSurname("James");
String fileName = "data.bin";
try (ObjectOutputStream os = new ObjectOutputStream(new FileOutputStream(fileName))) {
    os.writeObject(user);
} catch (IOException ex) {
    Logger.getLogger(Library.class.getName()).log(Level.SEVERE, null, ex);
}

一切都很完美,但如果我这样做的话:

Book book = new Book("Dan Brown", "Angels and Demons", 1);
Picked pck = new Picked(book, 20, 2);
user.add(pck);

然后我想序列化对象用户,程序崩溃了.我得到的输出是:

java.io.NotSerializableException:at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1183)at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)at java.util.ArrayList.writeObject(ArrayList.java:742) )sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)at java.lang.reflect. java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream)中的java.io.Object.StartClass.Drite中的java.io.Object.OutputStream.writeSerial上的java.io.Object.OutputStream.writeSerial中的方法. .java:1431)at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1177)at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1547)at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1508)在java.io.ObjectOutput java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:347)中的java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1177)中的Stream.writeOrdinaryObject(ObjectOutputStream.java:1431)

Answer 1

Picked并且Book还需要实施Serializable.