Who can answer these simple questions?

Question

Please be patient to read the following simple code. The numbers at the beginning of each line are line number. It is part of a code to read record into a file.
// Fig. 17.4: BankAccountRecord.java
1 public class BankAccountRecord implements Serializable {
2 private int account;
3 private String firstName;
4 private String lastName;
5 private double balance;
public BankAccountRecord()
6 this( 0, "", "", 0.0 );
public BankAccountRecord( int acct, String first,
String last, double bal )
7 setAccount( acct );
8 setFirstName( first );
9 setLastName( last );
10 setBalance( bal );
public void setAccount( int acct )
11 account = acct;
public void setFirstName( String first )
12 firstName = first;
public void setLastName( String last )
13 lastName = last;
public void setBalance( double bal )
14 balance = bal;
import BankAccountRecord;
public class CreateSequentialFile extends JFrame {
private ObjectOutputStream output;
15 File fileName = fileChooser.getSelectedFile();
16 output = new ObjectOutputStream(
new FileOutputStream( fileName ) );
public void addRecord()
17 int accountNumber = 0;
18 BankAccountRecord record;
19 String fieldValues[] = new String(4);
20 record = new BankAccountRecord(
accountNumber, fieldValues[ 1 ],
fieldValues[ 2 ],
fieldValues[ 3 ] );
21 output.writeObject( record );
22 output.flush();
My questions are:
1. BankAccountRecord is a class. After line 18 is excecuted,
record is an object of BankAccountRecord, right?
2. Line 20 initialize record, right?
3. After line 21 is excecuted, what is written to the file?
It should the record(account, firstName, lastName, balance),
right? But since BankAccountRecord is a class and record is an object of BankAccountRecord, how about the methods
of the class BankAccountRecord, for example setAccount( ),
setFirstName(), setLastName(), setBalance(), are these
methods also written into the file? I think not. But why?

Answer 1

1) After line 18, record is a reference to a BankAccountRecord with an undefined value. That is, it may be null, it may hold garbage, but you can't use it. Local variables are not initialized. Members are initialized to (0, 0.0, false, null) as appropriate for type, as are array elements.
2) Line 20 assigns record to refer to a newly created BankAccountRecord object.
3) Methods are not written out on serialization, only the state of the object--i.e. it's member variables. The method definitions are stored in the .class file that was created when you compiled the class. (If you really wanted to you could override the method (writeObject, I think) and write out whatever you wanted, but there's not need to serialize the method definitions, since they're part of the class.)