CODEWITHSUNDEEP
javalambdajava-8java-stream
Yadvendra Rathore
Yadvendra Rathore

Reputation: 73

Java Stream: Filter with multiple ranges

I'm trying to filter a resource and exclude some elements based on a field. To exclude I have a set (that contains a id that needs to be excluded) and a list (it contains multiple range of ids that needs to be excluded). I wrote the below logic and I'm not satisfied with the 2nd filter logic. Is there any better way we can do it with Java 8? I need to do the same for including ranges as well.

Set<String> extensionsToExclude = new HashSet<>(Arrays.asList("20","25","60","900"));
List<String> rangesToExclude = new ArrayList<>(Arrays.asList("1-10","20-25","50-70","1000-1000000"));
return directoryRecords.stream()
        .filter((directoryRecord) -> !extensionsToExclude.contains(directoryRecord.getExtensionNumber()))
        .filter((directoryRecord -> {
            Boolean include = true;
            for(String s : rangesToExclude) {
                String [] rangeArray = s.split("-");
                Integer extension = Integer.parseInt(directoryRecord.getExtensionNumber());
                if(extension <= Integer.parseInt(rangeArray[0]) && extension >= Integer.parseInt(rangeArray[1])) {
                    include = false;
                }
            }
            return include;
        }))
        .collect(Collectors.toList());

Thanks :)

Upvotes: 7

Views: 1774

Answers (3)

lczapski
lczapski

Reputation: 4120

I would suggest similar to ernest_k's answer with Range.

But in this approach you can use both collection to create List<Range> (this "20" can be treated as "20-20") and change the filter condition to use negation with anyMatch.

List<Range> ranges = Stream.concat(extensionsToExclude.stream(), rangesToExclude.stream())
        .map(Range::creatRange).collect(Collectors.toList());

return directoryRecords.stream()
        .filter(directoryRecord -> !ranges.stream()
                .anyMatch(r -> r.isInRange(
                        Integer.parseInt(directoryRecord.getExtensionNumber()))
                ))
        .collect(Collectors.toList());

class Range {
    private int start;
    private int end;

    Range(String start, String end) {
        this.start = Integer.parseInt(start);
        this.end = Integer.parseInt(end);
    }

    static Range creatRange(String range) {
        if (range.contains("-")) {
            return new Range(range.split("-")[0], range.split("-")[1]);
        }
        return new Range(range, range);
    }

    boolean isInRange(int n) {
        return start <= n && n <= end;
    }
}

UPDATE

Creation of List<Range> ranges can be change to remove points from Set<String> extensionsToExclude that are in the range created from List<String> rangesToExclud. Then unnecessary ranges will not be created.

List<Range> ranges = rangesToExclude.stream().map(Range::creatRange)
        .collect(Collectors.toCollection(ArrayList::new));
extensionsToExclude.stream()
        .filter(v -> !ranges.stream()
                .anyMatch(r -> r.isInRange(Integer.parseInt(v))))
        .map(Range::creatRange)
        .forEach(ranges::add);

Upvotes: 3

ernest_k
ernest_k

Reputation: 45309

I would do it with a custom Range class, something like:

class Range {
    private long start;
    private long end;

    Range(String start, String end) {
        this.start = Long.parseLong(start);
        this.end = Long.parseLong(end);
    }

    Range(String range) {
        this(range.split("-")[0], range.split("-")[1]);
    }

    boolean inRange(long n) {
        returns start <= n && n <= end;
    }
}

Which will make something like this possible:

List<Range> ranges = rangesToExclude.stream()
                     .map(Range::new).collect(Collectors.toList());
return directoryRecords.stream()
        .filter((directoryRecord) -> !extensionsToExclude
                                    .contains(directoryRecord.getExtensionNumber()))
        .filter(directoryRecord -> ranges.stream()
                                    .noneMatch(r -> r.isInRange(directoryRecord)))
        .collect(Collectors.toList());

I personally find your first filter good enough to be preserved as is.

Upvotes: 8

Angel Koh
Angel Koh

Reputation: 13485

you can do an early break if the range condition is true, rather than wait for all the entries to be evaluated.

if(extension >= Integer.parseInt(rangeArray[0]) && extension <= Integer.parseInt(rangeArray[1])) {
                    return true;
                }

otherwise just return false after the for loop.

Upvotes: 0

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