How to highlight first different line in a quite long String?

Question

I have user readable file with several hundreds rows. Each row is quite short(~20-30 symbols).

From time to time I need to execute equals operation with that string against another strings.

If Strings are different I need to find first row which differs. Sure I can do it manually:

in a loop find first character which differs then find previous and following '/n' but this code is not beaiful from my point of view.

Is there any other way to achieve it using some external libraries ?

Answer 1

There's no need for any library, what you ask is rather straightforward. But it's unique enough that no library would have it, so just write it yourself.

import java.nio.file.Files;
import java.util.*;

...

Optional<String> findFirstDifferentLine(Path file, Collection<String> rows) throws IOException {
  try (var fileStream = Files.lines(file)) { // Need to close
    var fileIt = fileStream.iterator();
    var rowIt = rows.iterator();
    while (fileIt.hasNext() && rowIt.hasNext()) {
      var fileItem = fileIt.next();
      if (!Objects.equal(fileItem, rowIt.next()) {
        return Optional.of(fileItem);
      }
    }
    return Optional.of(fileIt)
        .filter(Iterator::hasNext)
        .map(Iterator::next);
  }
}