Hi everyone. I'm writing a little Java program (it's an ImageJ plugin, but the problem is not specifically ImageJ related) and I have some problem, most probably due to the fact that I never really programmed in Java before...

So, I have a Vector of Vectors and I'm trying to save it to a file and read it.

The variable is defined as:

Vector <Vector <myROI> > ROIs = new Vector <Vector <myROI> >();

where myROI is a class that I previously defined.

Now, to write the vector to a file I use:

void saveROIs()
    {
    SaveDialog save = new SaveDialog("Save ROIs...", imp.getTitle(), ".xroi");
    String name = save.getFileName();
    if (name == null)
        return;
    String dir = save.getDirectory();

    try
        {
        FileOutputStream fos = new FileOutputStream(dir+name);
        ObjectOutputStream oos = new ObjectOutputStream(fos);
            oos.writeObject(ROIs);
            oos.close();
        }
    catch (Exception e)
        {
        IJ.log(e.toString());
        }
    }

This correctly generates a binary file containing (I suppose) the object ROIs.

Now, I use a very similar code to read the file:

void loadROIs()
    {
    OpenDialog open = new OpenDialog("Load ROIs...", imp.getTitle(), ".xroi");

    String name = open.getFileName();
    if (name == null)
        return;
    String dir = open.getDirectory();

    try
        {
            FileInputStream fin = new FileInputStream(dir+name);
            ObjectInputStream ois = new ObjectInputStream(fin);
        ROIs = (Vector <Vector <myROI> >) ois.readObject(); // This gives error
            ois.close();
            }
    catch (Exception e)
        {
        IJ.log(e.toString());
        }
    }

But this function does not work.

First, I get a warning:

 warning: [unchecked] unchecked cast found   : java.lang.Object
 required: java.util.Vector<java.util.Vector<myROI>>
            ROIs = (Vector <Vector <myROI> >) ois.readObject();
                                                        ^

I Googled for that and see that I can suppress by prepending @SuppressWarnings("unchecked"), but this just makes things worst, as I get an error:

<identifier> expected
   ROIs = (Vector <Vector <myROI> >) ois.readObject();
        ^

In any case, if I omit @SuppressWarnings and ignore the warning, the object is not read and an exception is thrown

java.io.WriteAbortedException: writing aborted; java.io.NotSerializableException: myROI

Again Google tells me myROI needs to implements Serializable. I tried just adding implements Serializable to the class definition, but it is not sufficient. Can anyone give me some hints on how to procede in this case? Also, how to get rid of the typecast warning?