Java Reference
In-Depth Information
ȗ withdraw(double amount) (overrides BankAccount method)
ȗ deductFees() (new to CheckingAccount )
Next, let us implement these methods. The deposit method increments the
transaction count and deposits the money:
public class CheckingAccount extends BankAccount
{
public void deposit(double amount)
{
transactionCount++;
// Now add amount to balance
. . .
}
. . .
}
Now we have a problem. We can't simply add amount to balance :
public class CheckingAccount extends BankAccount
{
public void deposit(double amount)
{
transactionCount++;
// Now add amount to balance
balance = balance + amount; // Error
}
. . .
}
Although every CheckingAccount object has a balance instance field, that
instance field is private to the superclass BankAccount . Subclass methods have no
more access rights to the private data of the superclass than any other methods. If you
want to modify a private superclass field, you must use a public method of the
superclass.
A subclass has no access to private fields of its superclass.
How can we add the deposit amount to the balance, using the public interface of the
BankAccount class? There is a perfectly good method for that purposeȌnamely,
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