SortedMap.transformValues?

[Michael Nascimento]

Thanks a lot Brian for the prompt response. I do still have a question
though: if I got it right,  the constructor will be invoked potentially
several times. That being true, wouldn't using HashMap::new and wrapping
the return in a TreeMap as a final step likely be better performant?

Regards,
Michael
On 8 Feb 2013 16:10, "Brian Goetz" <brian.goetz at oracle.com> wrote:

> Well, it would if I wrote it right.  Let's try this again.
>
>  // Imperative way:
>  Map<K,V1> oldMap = ...
>  Map<K,V2> newMap = new TreeMap<K,V1>();
>  oldMap.entrySet().stream()
>        .forEach(e -> newMap.put(e.getKey(), f.apply(e.getvalue()));
>
>  // Collect way:
>  Map<K,V2> newMap
>       = oldMap.entrySet().stream()
>               .collect(joiningWith(k -> f.apply(oldMap.get(k)),
>                        TreeMap::new);
>
> To which I'll add:
>  // Concurrent way:
>  Map<K,V1> oldMap = ...
>  Map<K,V2> newMap = new ConcurrentSkipListMap<K,V1>();
>  oldMap.entrySet().**parallelStream()
>        .forEach(e -> newMap.put(e.getKey(), f.apply(e.getvalue()));
>
>  // Parallel functional way with map merging:
>  Map<K,V2> newMap
>       = oldMap.entrySet().**parallelStream()
>               .collect(joiningWith(k -> f.apply(oldMap.get(k)),
>                        TreeMap::new)));
>
>
> Is that enough choices?  :)
>
> On 2/8/2013 12:59 PM, Michael Nascimento wrote:
>
>> Thank you Brian, but this does not return a SortedMap. I can always
>> construct a new one with the result, but I wonder if that is the best
>> approach.
>>
>> Regards,
>> Michael
>>
>> On Fri, Feb 8, 2013 at 3:27 PM, Brian Goetz <brian.goetz at oracle.com>
>> wrote:
>>
>>> Er, the second example should be "keys()" not "entrySet()".  Sorry.
>>>
>>>
>>> On 2/8/2013 11:58 AM, Brian Goetz wrote:
>>>
>>>>
>>>> // Imperative way:
>>>> Map<K,V1> oldMap = ...
>>>> Map<K,V2> newMap
>>>>      = oldMap.entrySet().stream()
>>>>              .forEach(e -> newMap.put(e.getKey(),
>>>> f.apply(e.getvalue()));
>>>>
>>>> // Collector way (works in parallel!)
>>>> Map<K,V2> newMap
>>>>      = oldMap.entrySet().stream()
>>>>              .collect(joiningWith(k -> f.apply(oldMap.get(k)));
>>>>
>>>>
>>>> On 2/8/2013 11:42 AM, Michael Nascimento wrote:
>>>>
>>>>>
>>>>> Any chance of getting an updated version for b76?
>>>>>
>>>>> On Wed, Jan 16, 2013 at 3:57 PM, Michael Nascimento <misterm at gmail.com
>>>>> >
>>>>> wrote:
>>>>>
>>>>>>
>>>>>> Hi guys,
>>>>>>
>>>>>> What is the lambda way of achieving:
>>>>>>
>>>>>>
>>>>>> http://docs.guava-libraries.**googlecode.com/git/javadoc/**
>>>>>> com/google/common/collect/**Maps.html#transformValues(**
>>>>>> java.util.SortedMap<http://docs.guava-libraries.googlecode.com/git/javadoc/com/google/common/collect/Maps.html#transformValues(java.util.SortedMap>
>>>>>> ,
>>>>>> com.google.common.base.**Function)
>>>>>>
>>>>>> ?
>>>>>>
>>>>>> Regards,
>>>>>> Michael
>>>>>>
>>>>>
>>>>>
>>>>>
>>>>
>>>