Java Reference
In-Depth Information
In some situations no reasonable flag value exists. For example, a class
for a stream of
double
values can contain any valid
double
, and there is
no possible end-of-stream marker. The most reasonable design is to add
an explicit
eof
test method that should be called before any read from
the stream:
while (!stream.eof())
process(stream.nextDouble());
stream.close();
On the other hand, continuing to read
past
the end of input is not ex-
pected. It means that the program didn't notice the end and is trying
to do something it should never attempt. This is an excellent case for a
ReadPastEndException
. Such behavior is outside the expected use of your
stream class, and throwing an exception is the right way to handle it.
Deciding which situations are expected and which are not is a fuzzy
area. The point is not to abuse exceptions as a way to report expected
situations.
Exercise 12.2
: Decide which way the following conditions should be
communicated to the programmer:
•
Someone tries to set the capacity of a
PassengerVehicle
object to
a negative value.
•
A syntax error is found in a configuration file that an object uses
to set its initial state.
•
A method that searches for a programmer-specified word in a
string array cannot find any occurrence of the word.
•
A file provided to an "open" method does not exist.
•
A file provided to an "open" method exists, but security prevents
the user from using it.
