Nice Java8 Streams

Java 8 Stream
I just threw a quick unit test together to see how a grep like tool would work in Java 8 using some nice streams stuff and this code looked so nice I thought I'd frame it an hang it on the web :)

@Test

public void testFindTxtFilesAndGetContentsThatMatchRegEx() throws IOException {

    Path start = Paths.get( "c:/temp" );

    BiPredicate<Path, BasicFileAttributes> bi = new BiPredicate<Path, BasicFileAttributes>() {

        @Override public boolean test(Path t, BasicFileAttributes u) {

            System.out.println( t );

            return t.toString().endsWith( "txt" );

        }

    };     

    System.out.println( Files.find( start, Integer.MAX_VALUE, bi )

            .filter( p -> Files.isRegularFile( p ) )

            .filter( p -> Files.isReadable( p ) )

            .map( this::myFunc )

            .collect( Collectors.joining() ) );

}

 

private String myFunc( final Path t ) {

    try {

        return Files.lines( t )

                .filter( p -> p.matches( ".*Hello.*" ) )

                .collect( Collectors.joining() );

    } catch ( IOException ioe ) {

        return "";

    }

}

 

 

I just really like the concise simplicity of this one :)

 

Sadly it was made on a Winblows machine so it's a dfs rooted at c:\temp that examines files with a .txt extension and reports any lines that match the regex ".*Hello.*"

 

so from this file structure

c:\temp

c:\temp\dest

c:\temp\source

c:\temp\source\dir1

c:\temp\source\dir1\dir3

c:\temp\source\dir1\dir3\New Text Document (2).txt

c:\temp\source\dir1\dir3\New Text Document.txt

c:\temp\source\dir1\New Text Document.txt

c:\temp\source\dir2

c:\temp\source\dir2\New folder

c:\temp\source\dir2\New folder\New folder

c:\temp\source\dir2\New folder\New folder\blob.txt

c:\temp\source\dir2\New folder\New folder\New folder

c:\temp\source\dir2\New folder\New folder\New folder\New Text Document.txt

c:\temp\source\dir2\New Text Document.txt

c:\temp\source\New Text Document.txt

The files c:\temp\source\dir2\New folder\New folder\blob.txt and c:\temp\source\New Text Document.txt have the content

blah blah Hello blah

Hello

some more

test

text

then another Hello

 

 So the output was

c:\temp

c:\temp\dest

c:\temp\source

c:\temp\source\dir1

c:\temp\source\dir1\dir3

c:\temp\source\dir1\dir3\New Text Document (2).txt

c:\temp\source\dir1\dir3\New Text Document.txt

c:\temp\source\dir1\New Text Document.txt

c:\temp\source\dir2

c:\temp\source\dir2\New folder

c:\temp\source\dir2\New folder\New folder

c:\temp\source\dir2\New folder\New folder\blob.txt

c:\temp\source\dir2\New folder\New folder\New folder

c:\temp\source\dir2\New folder\New folder\New folder\New Text Document.txt

c:\temp\source\dir2\New Text Document.txt

c:\temp\source\New Text Document.txt

blah blah Hello blahHellothen another Helloblah blah Hello blahHellothen another Hello

 

So you can see it duplicated the lines containing Hello because they were found in 2 files, it didn't print any lines that didn't contain Hello from any other files in very little code.

 

Just thought I'd share :)