使用readObject獲取byte [] []，從而提供OptionalDataException

Question

我在讀取某些文件時遇到了一個小問題。 我正在制作游戲，並決定為地圖創建自己的文件類型。 我做了一個特殊的應用程序來制作這些地圖文件。 實例化地圖后，我可以選擇調用readFile（String path）來將地圖設置為已保存的地圖。 我知道我必須以相同的順序讀取和寫入流，並且一切順利，直到我添加了有關讀取和寫入byte [] []的語句。 我無法弄清楚為什么會收到此異常，以及如何仍然讀取byte [] []。 這是我的課。

public class Map implements Serializable{

    String savePath;
    int boxWidth;
    int boxHeight;
    int mapWidth;
    int mapHeight;
    BufferedImage map;
    byte[][] encoded;
    LinkedList<BufferedImage> tileSet = new LinkedList<BufferedImage>();

    Map(int boxWidth, int boxHeight, int mapWidth, int mapHeight){
        map = new BufferedImage(boxWidth * mapWidth, boxHeight * mapHeight, BufferedImage.TYPE_INT_RGB);
        Graphics g = map.createGraphics();
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, map.getWidth(), map.getHeight());
        g.dispose();
        this.boxHeight = boxHeight;
        this.boxWidth = boxWidth;
        this.mapHeight = mapHeight;
        this.mapWidth = mapWidth;
        initEncode();
    }

    Map(){
        map = new BufferedImage(1, 1, BufferedImage.TYPE_INT_ARGB);
        this.boxHeight = 0;
        this.boxWidth = 0;
        this.mapHeight = 0;
        this.mapWidth = 0;
        initEncode();
    }

    void initEncode(){
        int width = 2 * mapWidth + 1;
        int height = 2 * mapHeight + 1;
        encoded = new byte[width][height];
        for(int i = 0; i < width; i++){
            for(int j = 0; j < height; j++){
                encoded[i][j] = 0;
            }
        }
    }

    void setMapTile(int i, int j, byte index){
        encoded[2 * i + 1][2 * j + 1] = index;
    }

    void setMapWall(int i, int j, byte index){
        encoded[2 * i][2 * i] = index;
    }

    void addToTileset(Tile tile){
        tileSet.add(tile.tile);
        writeFile(savePath);
    }

    //writing to file with path - boolean is for whether it went successfully or not
    boolean writeFile(String path){
        savePath = path;
        try{
            OutputStream file = new FileOutputStream(path);
            OutputStream buffer = new BufferedOutputStream(file);
            ObjectOutputStream output = new ObjectOutputStream(buffer);

            writeObject(output);

            output.close();
            buffer.close();
            file.close();
        }catch(IOException ex){
            System.err.println("Could not Write to file: " + path + "\nError caused by: " + ex);
            return false;
        }
        return true;
    }

    //reading from file with path - boolean is for whether it went successfully or not
    boolean readFile(String path){
        savePath = path;
        try{
            InputStream file = new FileInputStream(path);
            InputStream buffer = new BufferedInputStream(file);
            ObjectInputStream in = new ObjectInputStream(buffer);

            readObject(in);
            initEncode();

            file.close();
            buffer.close();
            in.close();
        }catch(IOException ex){
            System.err.println("Could not read from file: " + path + "\nError caused by: " + ex + "\n");
            ex.printStackTrace();
            return false;
        }catch(ClassNotFoundException e){
            System.err.println("Could not read from file: " + path + "\nError caused by: " + e + "\n");
            e.printStackTrace();
        }
        return true;
    }

    private void writeObject(ObjectOutputStream out) throws IOException {
        out.writeInt(boxHeight);
        out.writeInt(boxWidth);
        out.writeInt(mapHeight);
        out.writeInt(mapWidth);

        ImageIO.write(map, "png", out);
        out.writeObject(encoded);

        out.writeInt(tileSet.size());
        for(BufferedImage b: tileSet){
            ImageIO.write(b, "png", out);
         }
    }

    public void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException{
        boxHeight = in.readInt();
        boxWidth = in.readInt();
        mapHeight = in.readInt();
        mapWidth = in.readInt();

        map = ImageIO.read(in);
        encoded = (byte[][]) in.readObject();

        int tileSetSize = in.readInt();
        for(int i = 0; i < tileSetSize; i++){
            tileSet.add(ImageIO.read(in));
        }
    }
}

是否有某些原因導致我的（byte [] []）readObject（）行引發OptionalDataException，以及如何仍然讀/寫我的byte [] []。

編輯：謝謝您的回答Abhinav Kumar。 我忽略了這一點，但是當我修復代碼時，它仍然在同一行上給了我同樣的錯誤。 （該課程現已修復）。

Answer 1

您必須以與在流中寫入的順序和格式相同的順序讀取InputStream，否則將獲得OptionalDataException

您已按以下順序將數據寫入OutputStream：

        ImageIO.write(map, "png", out);
        out.writeInt(2 * mapWidth + 1);
        out.writeObject(encoded);

並且您正在按順序讀取流：-

        map = ImageIO.read(in);
        encoded = (byte[][]) in.readObject();

您在讀取地圖后只需讀取int。正確的代碼將是：-

 public void readObject(ObjectInputStream in) throws IOException, ClassNotFoundException{
        boxHeight = in.readInt();
        boxWidth = in.readInt();
        mapHeight = in.readInt();
        mapWidth = in.readInt();
        map = ImageIO.read(in);
        in.readInt();// you read this int and assign it to the object as you wish
        encoded = (byte[][]) in.readObject();
        int tileSetSize = in.readInt();
        for(int i = 0; i < tileSetSize; i++){
            tileSet.add(ImageIO.read(in));
        }
    }