How to unite data from several files in ONE buffer?

Question

I'd like create one Stream with data from several files. How I can do it ? There are my java class. Or maybe I should using not BufferReader but other way ? Thanks !!

import java.io.BufferedReader;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileReader;
import java.util.stream.Stream;

public class BuffReader {

public static void main(String[] args) throws FileNotFoundException {
    File file1 = new File("src/page_1.txt");
    File file2 = new File("src/page_2.txt");
    File file3 = new File("src/page_3.txt");
    BufferedReader bufferedReader = new BufferedReader(new FileReader(file1));

    //*** I'd like get one bufferedReader with file1 + file2 + file3.

    Stream<String> stream = bufferedReader.lines(); // get Stream
    stream.forEach(e -> System.out.println(e)); // Working with Stream
}
}

Answer 1

You can create one Stream from the BufferedReader for each file, combine them into a stream, and then use the Stream#flatMap method to create a stream that is a concatenation of all these.

import java.util.function.Function;
import java.util.stream.Stream;

public class CombinedStreams
{
    public static void main(String[] args)
    {
        Stream<String> stream0 = Stream.of("line0", "line1");
        Stream<String> stream1 = Stream.of("line2", "line3");
        Stream<String> stream2 = Stream.of("line4", "line5");

        Stream<String> stream = Stream.of(stream0, stream1, stream2)
            .flatMap(Function.identity());

        stream.forEach(e -> System.out.println(e)); 
    }
}

(Kudos to diesieben07 for the suggested improvement!)

Answer 2

If you don't need a BufferedReader and the Stream solution is enough, use that. If you absolutely need a Reader you can use SequenceInputStream to concatenate the InputStreams and then create a BufferedReader from that. The API is a little clunky since SequenceInputStream takes an Enumeration, so you would have to use one of the old collection types like Vector to construct it, but it works.