Java Reference
In-Depth Information
System.out.println("Removing all the coins:");
int
amountRemoved = 0;
while
(!myBank.isEmpty())
{
Coin removedCoin = myBank.remove();
System.out.println("Removed a " + removedCoin.getCoinName() +
".");
amountRemoved = amountRemoved + removedCoin.getValue();
}
// end while
System.out.println("All done. Removed " + amountRemoved +
" cents.");
}
// end main
private static void
addCoin(Coin aCoin, PiggyBank aBank)
{
if
(aBank.add(aCoin))
System.out.println("Added a " + aCoin.getCoinName() + ".");
else
System.out.println("Tried to add a " + aCoin.getCoinName() +
", but couldn't");
}
// end addCoin
}
// end PiggyBankExample
Output
Added a PENNY.
Added a NICKEL.
Added a DIME.
Added a QUARTER.
Removing all the coins:
Removed a QUARTER.
Removed a DIME.
Removed a NICKEL.
Removed a PENNY.
All done. Removed 41 cents.
Note:
A method can change the state of an object passed to it as an argument
You pass two arguments to the method
addCoin
: a coin and a piggy bank. Both of these argu-
ments are references to objects that exist in the
main
method. The method
addCoin
stores copies
of these references in its parameters, which, as you will recall, behave as local variables.
Although
addCoin
cannot change the references, because they exist in the
main
method, it can
alter the state of the referenced objects. In particular, it changes the piggy bank —that is, the
PiggyBank
object —by adding coins to it. That bank, remember, is local to
main
and is out-
side of
addCoin
.
