Can Someone Tell Me Why...

this will not compile? Am I missing something?

import javax.swing.JOptionPane;
import SavingsAccount;

public class SavingsAccountDriver //extends SavingsAccount
{

public static void main( String args[] )
{
String output;

SavingsAccount saver1, saver2;

// saver 1

saver1 = new SavingsAccount( 10000 );
output = "Savings Balance: " + saver1.toString();

saver1.calculateMonthlyInterest();
output += "\nSavings 1 w/ Interest: " + saver1.toString();

saver1.modifyInterest();
saver1.calculateMonthlyInterest();

output += "\nSavings 1 w/ Mod Interest: " + saver1.toString();

//saver 2

//output += "\n\n\nAnnual Interest Rate " + annualInterestRate;
//output += "\n\n\nMonthly Interest " + monthlyInterest;

saver2 = new SavingsAccount( 20000 );
output += "\n\nSavings Balance 2: " + saver2;

saver2.calculateMonthlyInterest();

output += "\nSavings 2 w/ Interest: " + saver2.toString();

saver2.modifyInterest();
saver2.calculateMonthlyInterest();

output += "\nSavings 2 w/ Mod Interest: " + saver2.toString();

// output
JOptionPane.showMessageDialog( null, output,
"Savings Account Interest", JOptionPane.INFORMATION_MESSAGE);

}
} // end class