java - 输出对象到文件

Question

我正在寻找一种将实例化类(对象)输出到文件的方法。我尝试过使用 FileStream，但它似乎不起作用。经过研究，似乎我需要使用一种称为“序列化”的技术。我对这个话题完全迷失了。有人可以帮我调试这段代码吗？我有一种预感，问题的发生是因为我试图在普通类中序列化抽象类。抽象类是java.util.Calendar。

class CalendarL implements java.io.Serializable{
    private static final long serialVersionUID = 1L;

    java.util.Calendar calendar;

    CalendarL (int date, int month, int year){
        calendar.set (Calendar.DATE, date);
calendar.set (Calendar.MONTH, month);
calendar.set (Calendar.YEAR, year);
    }
}

class IO {
    protected CalendarL reader() throws IOException, ClassNotFoundException{
        FileInputStream data = new FileInputStream("data.dat");
        ObjectInputStream dataObject = new ObjectInputStream(data);

        CalendarL calendar = (CalendarL)dataObject.readObject();

        dataObject.close();
        data.close();

        return calendar;
    }


    protected void output(CalendarL calendar) throws IOException, WriteAbortedException, NotSerializableException {
        new FileOutputStream("data.dat").close();

        FileOutputStream data = new FileOutputStream("data.dat");
        ObjectOutputStream dataObject = new ObjectOutputStream(data);

        dataObject.writeObject(calendar);
        dataObject.close();
        data.close();
   }

}

这是我得到的错误:

Exception in thread "main" java.io.NotSerializableException: hotelres.ClientL
at java.io.ObjectOutputStream.writeObject0(Unknown Source)
at java.io.ObjectOutputStream.defaultWriteFields(Unknown Source)
at java.io.ObjectOutputStream.writeSerialData(Unknown Source)
at java.io.ObjectOutputStream.writeOrdinaryObject(Unknown Source)
at java.io.ObjectOutputStream.writeObject0(Unknown Source)
at java.io.ObjectOutputStream.writeObject(Unknown Source)

Answer 1

I have a hunch that the problem is occurring because I am trying to serialize an abstract class within a normal class. The abstract class is java.util.Calendar.

这种预感是不正确的。您序列化实例(而不是类)，并且实例的类不能是抽象类。此外，Calendar 类确实实现了Serialized ... javadoc 是这么说的。