use of lambda and streams on nested object

public static Result match(Response rsp) throws Exception {
    Map<Boolean, List<Object>> collect = rsp.getFirstNodes().stream()
            .flatMap(firstNode -> firstNode.getSndNodes().stream()) // create stream of SndNodes
            .filter(SndNode::isValid) // filter so we only have valid nodes
            .map(node -> {
                // try to parse each node and return either the result or the exception
                try {
                    return parse(node);
                } catch (ParseException e) {
                    return e;
                }
            }) // at this point we have stream of objects which may be either Result or ParseException
            .collect(Collectors.partitioningBy(o -> o instanceof Result)); // split the stream into two lists - one containing Results, the other containing ParseExceptions

    if (!collect.get(true).isEmpty()) {
        return (Result) collect.get(true).get(0);
    }
    if (!collect.get(false).isEmpty()) {
        throw (Exception) collect.get(false).get(0); // throws first exception instead of last!
    }
    return null;
}

private static class IntermediateResult {

    private final SndNode node;
    private final Result result;
    private final List<ParseException> exceptions;

    private IntermediateResult(SndNode node, Result result, List<ParseException> exceptions) {
        this.node = node;
        this.result = result;
        this.exceptions = exceptions;
    }

    private Result getResult() throws ParseException {
        if (result != null) {
            return result;
        }
        if (exceptions.isEmpty()) {
            return null;
        }
        // this will show all ParseExceptions instead of just last one
        ParseException exception = new ParseException(String.format("None of %s valid nodes could be parsed", exceptions.size()));
        exceptions.stream().forEach(exception::addSuppressed);
        throw exception;
    }

}

public static Result match(Response rsp) throws Exception {
    return Stream.concat(
                    Arrays.stream(new SndNode[] {null}), // adding null at the beginning of the stream to get an empty "aggregatedResult" at the beginning of the stream
                    rsp.getFirstNodes().stream()
                            .flatMap(firstNode -> firstNode.getSndNodes().stream())
                            .filter(SndNode::isValid)
            )
            .map(node -> new IntermediateResult(node, null, Collections.<ParseException>emptyList()))
            .reduce((aggregatedResult, next) -> {
                if (aggregatedResult.result != null) {
                    return aggregatedResult;
                }

                try {
                    return new IntermediateResult(null, parse(next.node), null);
                } catch (ParseException e) {
                    List<ParseException> exceptions = new ArrayList<>(aggregatedResult.exceptions);
                    exceptions.add(e);
                    return new IntermediateResult(null, null, Collections.unmodifiableList(exceptions));
                }
            })
            .get() // aggregatedResult after going through the whole stream, there will always be at least one because we added one at the beginning
            .getResult(); // return Result, null (if no valid nodes) or throw ParseException
}

private static class ParsedNode {
    private final Result result;

    private ParsedNode(Result result) {
        this.result = result;
    }
}

public static Result match(Response rsp) throws Exception {
    return rsp.getFirstNodes().stream()
            .flatMap(firstNode -> firstNode.getSndNodes().stream())
            .filter(SndNode::isValid)
            .map(node -> {
                try {
                    // will parse all nodes because of flatMap
                    return new ParsedNode(parse(node));
                } catch (ParseException e ) {
                    return new ParsedNode(null);
                }
            })
            .filter(parsedNode -> parsedNode.result != null)
            .findFirst().orElse(new ParsedNode(null)).result;
}

Map<String, BigInteger> map =
    fromDB().stream()
            .collect(Collectors.toMap(
                o -> (String) o[0],
                o -> (BigInteger) o[1],
                (b1, b2) -> b2
            ));

List<Deal> output =
    dl.stream()
      .filter(d -> d.getDealop().stream().allMatch(po -> po.getColor().equals("red")))
      .collect(Collectors.toList());

int sum = Stream.of(obj1, obj2, obj3)
        .filter(o -> Objects.nonNull(o.getRootCategory()))
        .mapToInt(c -> c.getQty() * c.getPrice())
        .sum();

List<List<GrayscalePixel>> grayscalePhoto = 
    photo.stream().map(x ->
        x.stream().map(RGBpixel::convertToGrayscale).collect(Collectors.toList())
    ).collect(Collectors.toList());