使用ObjectInputStream.ReadObject（）Java optionalDataException

Question

我写给磁盘的对象类的定义如下：

public class EntityTableLink implements Index<Id, List<String>>, Serializable
{
    private Map<Id, Map<String, List<Pair<Integer, Integer>>>> idx;

    public EntityTableLink()
    {
        this.idx = new HashMap<>();
    }

    // Some getters and manipulation methods...
}

我编写类的实例 entityTableLink ，称其为 obj ，以磁盘为以下方式：

private void save() throws IOException
{
    ObjectOutputStream outputStream = new ObjectOutputStream(new FileOutputStream("object_file"));
    outputStream.writeObject(obj);
    outputStream.flush();
    outputStream.close();
}

我读取对象从磁盘上以下方式：

private void read()
{
    try (ObjectInputStream stream = new ObjectInputStream(new FileInputStream("object_file")))
    {
        EntityTableLink obj = (EntityTableLink) stream.readObject();
    }

    catch (IOException | ClassNotFoundException e)
    {
        // Some exception handling
    }
}

此代码使用以下堆栈跟踪生成 optionalDataException ：

java.io.OptionalDataException
    at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1702)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:493)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:451)
    at java.base/java.util.HashMap.readObject(HashMap.java:1458)
    at java.base/jdk.internal.reflect.GeneratedMethodAccessor2.invoke(Unknown Source)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at java.base/java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:1175)
    at java.base/java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:2325)
    at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2196)
    at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1679)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:493)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:451)
    at java.base/java.util.HashMap.readObject(HashMap.java:1460)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.base/java.lang.reflect.Method.invoke(Method.java:566)
    at java.base/java.io.ObjectStreamClass.invokeReadObject(ObjectStreamClass.java:1175)
    at java.base/java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:2325)
    at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2196)
    at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1679)
    at java.base/java.io.ObjectInputStream.defaultReadFields(ObjectInputStream.java:2464)
    at java.base/java.io.ObjectInputStream.readSerialData(ObjectInputStream.java:2358)
    at java.base/java.io.ObjectInputStream.readOrdinaryObject(ObjectInputStream.java:2196)
    at java.base/java.io.ObjectInputStream.readObject0(ObjectInputStream.java:1679)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:493)
    at java.base/java.io.ObjectInputStream.readObject(ObjectInputStream.java:451)
    at dk.aau.cs.daisy.edao.loader.IndexReader.loadEntityTableLink(IndexReader.java:111)
    at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
    at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
    at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
    at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
    at java.base/java.lang.Thread.run(Thread.java:834)

indexreader.loadentityTableLink（）是将对象写入磁盘的类方法。

根据不同的来源，当我读取包含原始数据的对象时，就会发生此问题，但是我的类 entityTableLink 不包含原始数据。我已经成功编写并阅读了包含类似类型的成员的其他类。

EOF FLAG设置为True，这意味着EOF比预期的要早。这可能是什么原因？