SortedMap.transformValues?

[Brian Goetz]

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,
>>>>> com.google.common.base.Function)
>>>>>
>>>>> ?
>>>>>
>>>>> Regards,
>>>>> Michael
>>>>
>>>>
>>>
>>