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https://issues.apache.org/jira/browse/HBASE-19682?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16317349#comment-16317349
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Appy edited comment on HBASE-19682 at 1/9/18 12:29 AM:
-------------------------------------------------------
The test failures may indeed be not related since no common failures between
last two runs. --Thanks for the patch [~belugabehr]. Let me push it to master.--
On second thought, i don't think it's good idea to return a
Collections.emptyList(), which is an immutable object, from a function with
return type List<T>.
Image seeing a fn:
List<Foo> getBaseFoos() {...}
and doing
List<Foo> myFoos = getBaseFoos();
myFoos.add(myfoo1);
myFoos.add(myfoo2);
And getting runtime error that list is immutable.
Such an uncertainty in return type makes code readability very hard.
I think a simple rule to make things easier here is:
- when returning List<> type is imperative, one should return {{new
ArrayList<>(0)}} for empty cases.
- when return type doesn't necessarily has to be List<>, it should be changed
to Iterable<> as return type and then {{return Collections.emptyList()}} can be
used.
In this case, can you please change the return types of relevant functions to
Iterable<>.
When the returned valued is used as stream, do as [this
stackoverflow|https://stackoverflow.com/questions/23114015/why-does-iterablet-not-provide-stream-and-parallelstream-methods?rq=1]
suggests. I agree that readability is less when using StreamSupport, but in
tradeoff of uncertainty and readability, i think there's a clear choice.
Thanks.
was (Author: appy):
The test failures may indeed be not related since no common failures between
last two runs. --Thanks for the patch [~belugabehr]. Let me push it to master.--
On second thought, i don't think it's good idea to return a
Collections.emptyList(), which is an immutable object, from a function with
return type List<T>.
Image seeing a fn:
List<Foo> getBaseFoos() {...}
and doing
List<Foo> myFoos = getBaseFoos();
myFoos.add(myfoo1);
myFoos.add(myfoo2);
And getting runtime error that list is immutable.
Such an uncertainty in return type makes code readability very hard.
I think a simple rule to make things easier here is:
- when returning List<> type is imperative, one should return {{new
ArrayList<>(0)}} for empty cases.
- when return type doesn't necessarily has to be List<>, it should be changed
to Iterable<> as return type and then {{return Collections.emptyList()}} can be
used.
In this case, can you please change the return types of relevant functions to
Iterable<>.
When the returned valued is used as stream, do as [this
stackoverflow|https://stackoverflow.com/questions/23114015/why-does-iterablet-not-provide-stream-and-parallelstream-methods?rq=1]
suggests.
Thanks.
> Use Collections.emptyList() For Empty List Values
> -------------------------------------------------
>
> Key: HBASE-19682
> URL: https://issues.apache.org/jira/browse/HBASE-19682
> Project: HBase
> Issue Type: Improvement
> Components: hbase
> Affects Versions: 3.0.0
> Reporter: BELUGA BEHR
> Assignee: BELUGA BEHR
> Priority: Minor
> Attachments: HBASE-19682.1.patch, HBASE-19682.2.patch,
> HBASE-19682.3.1.patch
>
>
> Use {{Collection.emptyList()}} for returning an empty list instead of
> {{return new ArrayList<> ()}}. The default constructor creates a buffer of
> size 10 for _ArrayList_ therefore, returning this static value saves on some
> memory and GC pressure and saves time not having to allocate a new internally
> buffer for each instantiation.
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