Guardar datos internamente en Android desordena mis datos

I'm currently working on a game, where I need to create a transposition table for my AI. I implemented Hashtable de manera que la key to the Hashtable is a state under consideration and its corresponding value is the optimal next move.

However, when I save the Hashtable in Android's internal storage and restore it next time, it seems to have some saved data, but the keys (i.e. game states) are different than the keys I have saved in the previous instance.

Here is how I save and restore my data:

    private void readTranspositionTableFromFile() {
        FileInputStream fis = openFileInput(FILENAME);
        ObjectInputStream ois = new ObjectInputStream(fis);
        transpositionTable = (Hashtable<BoardState, NextMove>) ois.readObject();

    private void writeTranspositionTableToFile() {
        FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE);
        ObjectOutputStream oos = new ObjectOutputStream(fos);

I see no problem in my hashCode() implementation, since it keeps returning same values for same states over and over.

I suspect saving/restoring the transposition table messes up my data because I logged the 2 runtimes and on the first one I got hashCode() to return 3964 and 3029 for the 2 states that were to be added to the table. However, while reading the table from file, the hashCode() returned 9119 twice.

Is there any problem in saving/restoring the data?

preguntado el 31 de julio de 12 a las 13:07

Maybe BoardState isn't correctly serialized? Have you verified that its members are correct after writing and reading to file? -

You implemented your Hashtable yourself? Why aren't you using HashMap? I never had serialization issues with it. Please add some code of the serialization process. -

@ekholm I just added implements Serializable to BoardState. Apart from that, my Board state just consists of few instance variables, getters, setters, hashCode() and equals(). @Martze No, I used the Tabla de picadillo from Java library (java.util.Hashtable). I haven't tried HashMap. -

Is that the correct way to serialize? -

For debugging, I would try writing a few BoardState objects one by one to an ObjectOutputStream, reading each object back with an ObjectInputStream, and verify that all fields are correct -

1 Respuestas

My serializing and hashing was completely fine. My program went something like this:

  1. add new key-value pair to transpositionTable
  2. play next move
  3. ahorrar transpositionTable to internal storage

However, after meticulous logging, I found that my transpositionTable changed after step 2). This was because during step 1), I used

BoardState newKey = currentData.getBoardState();

and saved it to my transpositionTable. Then in step 2), when my currentData changed, my transpositionTable changed accordingly. I tried using

BoardState newKey = currentData.getBoardState().clone();

but that didn't work either. Finally I had to assign each field of currentData.getBoardState() a newKey manually, which worked.

Respondido 01 ago 12, 13:08

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