Basic functional style question

[mohan.radhakrishnan at polarisFT.com]

Yes. Thanks Stuart. 

I also have these questions.

1. How do I apply a large number of regex patterns one by one in the same 
pipeline ? When is a new functional interface needed ?

2.  function(){
        return (data$V1[ grep ("(.*)Full GC(.*)", data[,1])])
     }

     Is there a way to do this ? This R code uses code to change values in 
a data structure in-place. Code and data are together here.

Mohan




From:   Stuart Marks <stuart.marks at oracle.com>
To:     mohan.radhakrishnan at polarisft.com, lambda-dev at openjdk.java.net
Date:   11/27/2013 01:46 PM
Subject:        Re: Basic functional style question



I started scratching this out and I got a sense of déjà vu, and then I 
realized 
Kirk Pepperdine recently wrote a blog post last week about using lambda to 
parse 
and pattern match GC logs. Were you at his talk at Øredev?

https://weblogs.java.net/blog/kcpeppe/archive/2013/11/10/fun-lambdas

The approach he ended up with (with help from Brian Goetz), applied to 
your 
example, would look something like this:

     Pattern pat = Pattern.compile("Current.*?[/|]");
     Files.lines(Paths.get(...))
          .map(pat::matcher)
          .filter(Matcher::find)
          .map(Matcher::group)
          .forEach(System.out::println);

Note this uses Pattern and Matcher instead of Scanner, as they're more 
flexible.

The insight is to map each input string to a Matcher so that midway 
through the 
pipeline we have Stream<Matcher>. We then filter the matchers to get only 
the 
successful ones, and then extract the matched string from them.

Does this do what you want?

s'marks

On 11/26/13 10:38 PM, mohan.radhakrishnan at polarisft.com wrote:
> Sent by mistake. The actual question is this.
>
> The code in the previous mail works but when I use 'R' language this is
> accomplished by this line.
>
> y <- apply( y, 1, function(z) str_extract(z,"Current.*?[/|]"))
>
> I can again operate on the data structure like this.
>
> z <- str_extract_all(y,"[0-9]+(/,|/|)")
>
> I think this is possible using Streams and filters.
>
> How should I use these lines without defining new Functional interfaces 
?
>
>          Scanner s = new Scanner( data );
>          s.findInLine("Current.*?[/|]");
>          System.out.println(s.match().group());
>
> Thanks.
>
>
>
> From:   Mohan Radhakrishnan/BSC31/polarisFT
> To:     lambda-dev at openjdk.java.net
> Date:   11/27/2013 11:57 AM
> Subject:        Basic functional style question
>
>
> Hi,
>
> This is a question from a user. I am trying to jdk 8 to parse a file and
> apply a regex on it.
>
> public class GCLogParser {
>
>      private void readFile() throws IOException {
>
>          Stream<String> s = Files.lines(get(("D:\\GC
> Analysis\\usage.txt")), UTF_8);
>          s.forEach( this::parse  );
>      }
>
>      public static void parseDocument(  Parseable parser,
>   String data){
>          parser.apply(data);
>      }
>      private void parse( String data ){
>
>          Scanner s = new Scanner( data );
>          s.findInLine("Current.*?[/|]");
>          System.out.println(s.match().group());
>      }
>
>      public static void main( String... argv ) throws IOException {
>          new GCLogParser().readFile();
>      }
>
>      @FunctionalInterface
>      public interface Parseable{
>           void apply( String s);
>      }
> }
>
>
>
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