writing object to internal storage

Question

I have succeeded in writing and reading a string to a file on my android app's internal storage, but I want to write an object and it's not working. I've read Oracle's documentation on the matter, which says for object fields to be transmitted over the stream the object needs to implement serializable, or something. I added imports serializable and implements serializable to the cat class but it threw an error. Without it "oos.writeObject(myCat);" causes an error too. I'm very confused.

The below code exists in a java activity class tied to a layout.xml. The user presses a button and the object is saved or loaded. As stated writing and reading a string seems to work fine, but objects less so.

   private void writeFile()
   {
      try
      {
         String myFile = "myFile";
         cat myCat = new cat("Harry", "blue", 11);

         FileOutputStream fos = openFileOutput(myFile,MODE_WORLD_READABLE);
         ObjectOutputStream oos = new ObjectOutputStream(fos);
         oos.writeObject(myCat);
         oos.close();
         fos.close();

         Toast.makeText(getBaseContext(),"object saved",Toast.LENGTH_SHORT).show();
      }
      catch (Exception e)
      {
         e.printStackTrace();
      }
}

And

   private void readFile()
   {
      try
      {
         String myFile = "myFile";

         FileInputStream fis = openFileInput(myFile);
         ObjectInputStream ois = new ObjectInputStream(fis);
         cat yourCat = (cat) ois.readObject();
         ois.close();
         fis.close();

         String output = yourCat.name + " the " + yourCat.colour + " cat";
         Toast.makeText(getBaseContext(),output,Toast.LENGTH_SHORT).show();
      }
      catch (Exception e)
      {

      }
}

The cat object

public class cat
{
   public String name = "";
   public String colour = "black";
   public int age = 0;

   public cat(String pName, String pColour, int pAge)
   {
      name = pName;
      colour = pColour;
      age = pAge;
   }
}

Answer 1

Try using:

MODE_PRIVATE

In the openFileOutput() method.

Answer 2

Adding "implements Serializable" to the cat class works. I'm not sure why it didn't in the first place. Sorry for the fuss.