search-stream-flux.java

import java.util.*;
import java.util.stream.Collectors;
import java.util.stream.Stream;
import reactor.core.publisher.*;
import reactor.core.scheduler.Schedulers;

public Flux<String> searchReactiveStream() {

    return Flux.create((FluxSink<String> fluxSink) -> {

        InputStream inputStream = null;
        try {
            inputStream = new FileInputStream(pathFile);
        } catch (FileNotFoundException e) {
            fluxSink.error(e);
        }

        BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream));

        Stream<String> linesStream = bufferedReader.lines();

        AtomicBoolean found = new AtomicBoolean(false);

        linesStream.forEach(l -> {
            if (l.contains(SEARCH_TOKEN)) {
                fluxSink.next(l);
                found.set(true);
            }
        });

        if (!found.get()) {
            fluxSink.next("No results found");
        }

        fluxSink.complete();

    });

}

related to medium article https://gae-piaz.medium.com/search-string-in-file-with-java-as-fast-as-possible-fedafdc7a3ee