Convert old "into" code to the collectors

[Paul Sandoz]

You are wiring up the wrong parameters to both toCollection and toList.

Here are the relevant methods:

    public static<T, C extends Collection<T>>
    Collector<T,C> toCollection(Supplier<C> collectionFactory) {
        return leftCombiningReducer(collectionFactory, Collection::add, Collection::addAll);
    }

    public static<T>
    Collector<T,List<T>> toList() {
        // @@@ Consider a tree-based List, if we can solve the post-processing problem
        return toCollection(ArrayList<T>::new);
    }

The former takes a supplier:

  Collectors.<...>toCollection(ArrayList<...>::new);

The latter takes no parameters:

  Collectors.<...>toList();

Notice how the latter calls the former.

Hth,
Paul.


On Jan 16, 2013, at 4:41 PM, Marcos Antonio <marcos_antonio_ps at hotmail.com> wrote:

> 
> Here are the compiler error messages for the two case:
> 
> List<PropriedadeChavePai> propriedadesChavePai = new ArrayList<>();
> 
> chave.getPropriedadesChavePai().stream().
>    map(PropriedadeChavePai::new).
>    collect(Collectors.<PropriedadeChavePai>toCollection(propriedadesChavePai));
> 
> [javac] C:\desenvolvimento\desktop\desenvolvimento\br\desenvolvimento\dados\CriadorChave.java:259: error: method toCollection in class Collectors cannot be applied to given types;
> [javac]       collect(Collectors.<PropriedadeChavePai>toCollection(propriedadesChavePai));
> [javac]                         ^
> [javac]   required: Supplier<C>
> [javac]   found: List<PropriedadeChavePai>
> [javac]   reason: actual and formal argument lists differ in length
> [javac]   where C,T are type-variables:
> [javac]     C extends Collection<T> declared in method <T,C>toCollection(Supplier<C>)
> [javac]     T extends Object declared in method <T,C>toCollection(Supplier<C>)
> [javac] 1 error
> 
> --------------------------------------------------------------------------
> 
> List<PropriedadeChavePai> propriedadesChavePai = new ArrayList<>();
> 
> chave.getPropriedadesChavePai().stream().
>    map(PropriedadeChavePai::new).
>    collect(Collectors.<PropriedadeChavePai>toList(propriedadesChavePai));
> 
> [javac] C:\desenvolvimento\desktop\desenvolvimento\br\desenvolvimento\dados\CriadorChave.java:259: error: method toList in class Collectors cannot be applied to given types;
> [javac]       collect(Collectors.<PropriedadeChavePai>toList(propriedadesChavePai));
> [javac]                         ^
> [javac]   required: no arguments
> [javac]   found: List<PropriedadeChavePai>
> [javac]   reason: actual and formal argument lists differ in length
> [javac] 1 error
> 
> Marcos
> 
> ----------------------------------------
>> Date: Wed, 16 Jan 2013 15:05:22 +0000
>> From: maurizio.cimadamore at oracle.com
>> To: marcos_antonio_ps at hotmail.com
>> CC: lambda-dev at openjdk.java.net
>> Subject: Re: Convert old "into" code to the collectors
>> 
>> On 16/01/13 14:34, Marcos Antonio wrote:
>>> Hello, everybody!
>>> 
>>> Before build b73 I had code like this:
>>> 
>>> List<PropriedadeChavePai> propriedades = new ArrayList<>();
>>> 
>>> chave.getPropriedadesChavePai().stream().
>>> map(PropriedadeChavePai::new).
>>> into(propriedades);
>>> 
>>> Now I'm having trouble trying to convert it to use the new Collectors. I have tried something like this:
>>> 
>>> chave.getPropriedadesChavePai().stream().
>>> map(PropriedadeChavePai::new).
>>> collect(Collectors.toCollection(propriedades));
>>> 
>>> but it didn't work and I couldn't figure out the right thing to do.
>>> 
>>> Thank you in advance.
>>> 
>>> Marcos
>>> 
>> What do you mean it didn't work? Did you get an error message from the
>> compiler? If so, can you please paste it?
>> 
>> Maurizio 		 	   		  
>