How to merge >1000 xml files into one using Java

Question

I am trying to merge many xml files into one. I have successfully done that in DOM, but this solution is limited to a few files. When I run it on multiple files >1000 I am getti

Answer 1

Just do it without any xml-parsing as it doesn't seem to require any actual parsing of the xml.

For efficiency do something like this:

File dir = new File("/tmp/rootFiles");
String[] files = dir.list();
if (files == null) {
    System.out.println("No roots to merge!");
} else {
        try (FileChannel output = new FileOutputStream("output").getChannel()) {
            ByteBuffer buff = ByteBuffer.allocate(32);
            buff.put("\n".getBytes()); // specify encoding too
            buff.flip();
            output.write(buff);
            buff.clear();
            for (String file : files) {
                try (FileChannel in = new FileInputStream(new File(dir, file).getChannel()) {
                    in.transferTo(0, 1 << 24, output);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
            buff.put("\n".getBytes()); // specify encoding too
            buff.flip();
            output.write(buff);
        } catch (IOException e) {
            e.printStackTrace();
        }