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https://issues.apache.org/jira/browse/MATH-1408?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15956477#comment-15956477
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Bruno P. Kinoshita commented on MATH-1408:
------------------------------------------
Hummm. Started working on the pull request, first identifying where CCE was
being used. But then realised it may not be that simple. Let's take Frequency
as example.
It has no generic types, but creates an internal TreeMap, with keys with the
type `Comparator<?>`. Then whenever you add or get values from the TreeMap, it
will throw CCE if you pass a key value with a different type from the others
stored in the map.
{code}
Frequency f = new Frequency();
// Okay
f.addValue("Ola");
// Key 12, type Integer, does not match String type. CCE, wrapped in a Math
exception
f.addValue(12);
{code}
And even a simpler example without Math classes to help outlining the issue.
{code}
TreeMap<Integer, String> map = new
int key = 1;
map.put(key, "One");
// Okay
map.get(100);
// TreeMap will try to call 1.1#compareTo against each Key it contains, which
can result
// in a CCE here.
map.get(1.1);
{code}
It is not clear to me how we could compare the key type to the given v value.
Checking if the map is not empty, and then checking the type of the first key
doesn't sound very elegant (and not sure if it would be a valid solution). I
guess an option to eliminate the CCE could be generify the Frequency class
maybe (though I didn't spend much time checking if that would work well), but
also not sure if that would work for the other cases of CCE.
Any ideas?
> Do not use exceptions for control flow
> --------------------------------------
>
> Key: MATH-1408
> URL: https://issues.apache.org/jira/browse/MATH-1408
> Project: Commons Math
> Issue Type: Task
> Reporter: Gilles
> Priority: Minor
> Labels: control, exception, flow
> Fix For: 4.0
>
>
> There are several occurrences where exception is used to control flow.
> Code such as
> {noformat}
> try {
> // block A
> } catch (ClassCastException e) {
> // block B
> }
> {noformat}
> where "block A" is trying to cast an object "o" to "SomeClass", should be
> changed to
> {noformat}
> if (o instanceof SomeClass) {
> // block A
> } else {
> // block B
> }
> {noformat}
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