The old good Java object serialization is available for you in Android. you can define Serializable classes like:
class Cirle implements Serializable {
final int radius;
final String name;
Circle(int radius, int name) {
this.radius = radius;
this.name = name;
}
}
and then write then to the ObjectOutputStream:
File myFile = new File(getFilesDir(), "myObjects.bin");
FileOutputStream out = new FileOutputStream(myFile);
ObjectOutputStream oout = new ObjectOutputStream(new BufferedOutputStream(out));
oout.writeObject(new Circle(10, "One"));
oout.writeObject(new Circle(12, "Two"));
oout.close()
Java object serialization may be either perfect or really bad choice, depending on what do you want to do with it - outside the scope of this tutorial and sometimes opinion based. Read about the versioning first if you decide to use it.