Question

我有以下代码来保存对象的ArrayList，然后再次读取它。但是它不起作用，读取显示为空。怎么解决？

一些细节：POInode实现seriazable;看起来数据被正确保存; arraylist是非静态的;

// READ & Write Class:

public GlobalWriteAndLoadPositions(){   
}
public void write(String folder, List<POInode> POIlist)  throws IOException {   

    int nextFileItarator = (int) Files.list(Paths.get(folder)).count();
    nextFileItarator++;
    FileOutputStream fout= new FileOutputStream(folder + nextFileItarator + ".txt");

    ObjectOutputStream oos = new ObjectOutputStream(fout);      
    oos.writeObject(POIlist);
    oos.close();

    // the next line shows the arraylist full of objects and the File looks fine. (non-clear text file, but full of data)
    POIlist.forEach((a)->System.out.print("POI " + a.ID + " @ (" + a.getPosition().xCoord +" , " + a.getPosition().yCoord + ") | " ));
    System.out.println("\n");
}


@SuppressWarnings("unchecked")
public ArrayList<POInode> load(String file)  throws IOException, ClassNotFoundException{

    FileInputStream fin = new FileInputStream(file);
    ObjectInputStream ois = new ObjectInputStream(fin);
    List<POInode> listOfLoadedPOIs = new ArrayList<POInode>();

    listOfLoadedPOIs = (ArrayList<POInode>) ois.readObject(); // THIS LOOK WRONG, I MEAN,it is my guess

    ois.close();    

    // the following command shows the correct size list, but empty values!
    listOfLoadedPOIs.forEach((a)->System.out.print("POI " + a.ID + " @ (" + a.getPosition().xCoord +" , " + a.getPosition().yCoord + ") | " ));
    System.out.println("\n");

    return (ArrayList<POInode>) listOfLoadedPOIs;   
}

//Class usage:

if (Global.shouldSavePoiDistribution){

        List<POInode> listOfPOIs = new ArrayList<POInode>();
        for(Node n : Runtime.nodes) {   
            if (n instanceof POInode){
                listOfPOIs.add((POInode) n);                    
            }
        }

        GlobalWriteAndLoadPositions saver = new GlobalWriteAndLoadPositions();
        saver.write(Global.distributionFolder,listOfPOIs);
    }

// lets load a distribution IFF asked to
if (Global.shouldLoadPoiDistribution){

    GlobalWriteAndLoadPositions loader = new GlobalWriteAndLoadPositions();
    try {
        Global.listOfLoadedPOIs = loader.load(Global.distributionFile);
    } catch (ClassNotFoundException e) {
        e.printStackTrace();
    }
}

Answer 1

问题是继承的变量。它不是Serializable作为类。我扩展了原始库。

从文件加载arraylist时清空对象

1 个答案: