Strange understanding of transient keyword

Question

Hi,
I'm currently studying for the SCJP exam and came across the following question.
"What can be done so that a Portfolio object can be serialized while preserving the state of the Bond objects contained in Portfolio?"
class Bond
    String ticker; double coupon; java.util.Date maturity;
class Portfolio implements Serializable
    String accountName;
    Bond[] bonds;
public class TestClass {
    public static void main(String[] args) throws Exception{
     Portfolio portfolio = // get portfolio somehow.
     // serialize porfolio
}One of the proposed solutions is "Implement readObject and writeObject methods in Portfolio and read and write the state of Bond object explicitly."
But I find the solution quite strange
class Bond  // does not implement Serializable
    String ticker = "bac"; double coupon = 8.3; java.util.Date maturity = new Date();
class Portfolio implements Serializable
    String accountName;
    transient Bond bonds = new Bond[]{ }; // must be transient because it cannot be serialized
    private void writeObject(ObjectOutputStream os) throws Exception{
     os.defaultWriteObject();
     os.writeObject(bonds.length);
     //write the state of bond objects
     for(int i=0; i<bonds.length; i++) {
          os.writeObject(bonds.ticker);
          os.writeDouble(bonds[i].coupon);
          os.writeObject(bonds[i].maturity);
private void readObject(ObjectInputStream os) throws Exception{
     os.defaultReadObject();
     int n = os.readInt();
     this.bonds = new Bond[n];
     //read the state of bond objects.
     for(int i=0; i<bonds.length; i++) {
          bonds[i] = new Bond();
          bonds[i].ticker = (String) os.readObject();     
          bonds[i].coupon = os.readDouble();
          bonds[i].maturity = (java.util.Date) os.readObject();
What I'm slightly confused is if the variable bonds is defined as transient, how can one write out the state explicitly?                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                       

Answer 1

Even given that Bond isn't serializable and Portfolio has-an array of bonds, it would have made more sense to stick the serializing code in a BondSerializer class, rather than embedding it in Portfolio. That way you could test it separately and reuse it outside of Portfolio.
Oh, this is a test question. Never mind...