Java Serialization for Extended Class

Java Serialization for Extended Class

In java serialization class Mp3player extends ElectronicDevice implements
Serializable in this code super class electronicdevice is not implemented
serializable. here super class is also getting serialized. my
understanding is super class is also gets serialized due to extends.let me
know my understanding is correct or not.
import java.io.*;
class ElectronicDevice { ElectronicDevice()
{ System.out.print("ed ");
}}
class Mp3player extends ElectronicDevice implements Serializable {
Mp3player() { System.out.print("mp "); }
}
class MiniPlayer extends Mp3player {
MiniPlayer() { System.out.print("mini "); }
public static void main(String[] args) {
MiniPlayer m = new MiniPlayer();
try {
FileOutputStream fos = new FileOutputStream("dev.txt");
Obje`enter code here`ctOutputStream os = new ObjectOutputStream(fos);
os.writeObject(m); os.close();
FileInputStream fis = new FileInputStream("dev.txt");
ObjectInputStream is = new ObjectInputStream(fis);
MiniPlayer m2 = (MiniPlayer) is.readObject();
is.close();
System.out.println();
} catch (Exception x) { System.out.print("x "); }
} }