How to write data into file using Serializable in java

This is simple example if writing data into file:

import java.io.*;

class AAA implements Serializable{
int x = 100;
int y = 200;
int z = 300;
public void disp(){
System.out.println("x = "+x);
System.out.println("y = "+y);
System.out.println("z = "+z);
}

}

public class ObjectTest1 {
public static void main(String[] args) throws Exception {
AAA ap = new AAA();

File f = new File("C:\\FileTest\\Obj.txt");
FileOutputStream fos = new FileOutputStream(f);
BufferedOutputStream bos = new BufferedOutputStream(fos);
ObjectOutputStream oos = new ObjectOutputStream(bos);

oos.writeObject(ap);
oos.close();
bos.close();
fos.close();

}

}