对象无法使用 ObjectInputStream 读取两次

Question

每当我最初写入文件时，一切都很好。当我将数据读入链表时，一切都很好。最后，当我保存文件时，文件内容与我刚刚写入它的初始文件匹配。

我

遇到的问题是，当我尝试从保存的文件中读取对象时(第二次运行程序后(，文件中的所有内容都被擦除，我无法读取任何对象。

public class MedicalInformation {
    public static void main(String[] args) throws FileNotFoundException, IOException, ClassNotFoundException, EOFException {

        Scanner userInput = new Scanner(System.in);
        System.out.println("Enter the file path");
        String filePath = userInput.next(); //"C:\Users\ag\Desktop\medicalData\patient.dat";
        System.out.println("The file's path is " + filePath);
        System.out.println("Enter the file name and its path you want to read in");
        // create objects that allow one to read and write to the file
        ObjectOutputStream out = new ObjectOutputStream(new FileOutputStream(filePath));
        ObjectInputStream in = new ObjectInputStream(new FileInputStream(filePath));
        //creates the objects to be written into the file
        Patient p1 = new Patient("Alex", "1123 metropolitan Queens NY 11385", new Date("11/20/1997"));
        p1.setFirstVisit(new Date("11/20/1997"));
        p1.setHeight(72);
        p1.setLastVisit(new Date("11/20/1997"));
        p1.setWeight(200);
        out.writeObject(p1);
        System.out.println(p1);
        Patient p2 = new Patient("John", "200 avenue of americas Manhttann 10111", new Date("12/20/1999"));
        p2.setFirstVisit(new Date("11/11/2005"));
        p2.setHeight(5);
        p2.setLastVisit(new Date("11/21/2010"));
        p2.setWeight(150);
        out.writeObject(p2);
        Patient p3 = new Patient("Sarah", "24 Park avenue Manhttann 10111", new Date("09/07/1960"));
        p3.setFirstVisit(new Date("05/11/1977"));
        p3.setHeight(75);
        p3.setLastVisit(new Date("01/21/2017"));
        p3.setWeight(110);
        out.writeObject(p3);
        Patient p4 = new Patient("Malcolm", "56street East NY 10444", new Date("05/28/1977"));
        p4.setFirstVisit(new Date("01/11/1990"));
        p4.setHeight(75);
        p4.setLastVisit(new Date("8/21/2016"));
        p4.setWeight(155);
        out.writeObject(p4);
        Patient p5 = new Patient("Johnny", "89 street Jamaica 12221", new Date("12/25/1944"));
        p5.setFirstVisit(new Date("03/16/1966"));
        p5.setHeight(55);
        p5.setLastVisit(new Date("5/21/2015"));
        p5.setWeight(355);
        out.writeObject(p5);
        Patient p6 = new Patient("Laura", "east 4th street Brooklyn 12214", new Date("08/08/1988"));
        p6.setFirstVisit(new Date("05/11/1999"));
        p6.setHeight(48);
        p6.setLastVisit(new Date("8/21/2012"));
        p6.setWeight(350);
        out.writeObject(p6);

        //put them into a list
        List < Patient > list = new List < Patient > ();

        boolean done = false;
        while (!done) {
            try {
                Patient patients = (Patient) in .readObject();
                list.add(patients);
                //an EOFException is thrown when the stream ends, which means the end of the file is reached
            } catch (EOFException e) {
                done = true;
                out.close(); in .close();
            }
        }


        if (option == 8) {
            System.out.println("Would you like to save the file y/n");
            saveFile = userInput.next();
            if (saveFile.equals("y")) {
                //save file
                System.out.println("Enter the file's name where it is to be saved");
                filePath = userInput.next();
                out = new ObjectOutputStream(new FileOutputStream(filePath));
                LLNode < Patient > p = list.getList();
                while (p != null) {
                    out.writeUnshared(p.getInfo());
                    p = p.getLink();
                }
            } else {
                System.out.println("You chose not to save the file");
            }
            out.close(); in .close();
            break;
        }
    }
}
}

所以我要做的是输入文件名C：\Users\ag\Desktop\medicalData\patient.dat然后六个对象被写入其中。

然后我将它们读入链表

我不执行任何操作

我将链表保存到文件 C：\Users\ag\Desktop\medicalData\patient.dat

我

注释掉了将 6 个对象写入文件，现在我只想阅读它们。这就是我的问题所在，我最终留下了一个包含两个字符的文件，并且无法获得 EOFException。

Answer 1

序列化同一对象将反序列化同一对象，即使您在发送端更改了它。您需要使用以下之一：

• ObjectOutputStream.reset()
• ObjectOutputStream.writeUnshared()
• ObjectInputStream.readUnshared() .