[BUG] DocumentSplitter‘s maxOverlapSize parameter sometimes fails

[xbzhang1994]

DocumentSplitter‘s maxOverlapSize parameter sometimes fails .
Look at this method: dev.langchain4j.data.document.splitter.HierarchicalDocumentSplitter#overlapFrom

private String overlapFrom(String segmentText) {
        if (maxOverlapSize == 0) {
            return "";
        }

        SegmentBuilder overlapBuilder = new SegmentBuilder(maxOverlapSize, this::sizeOf, joinDelimiter());

        String[] sentences = new DocumentBySentenceSplitter(1, 0, null, null).split(segmentText);
        for (int i = sentences.length - 1; i >= 0; i--) {
            String part = sentences[i];
            if (overlapBuilder.hasSpaceFor(part)) {
                overlapBuilder.prepend(part);
            } else {
                return overlapBuilder.build();
            }
        }

        return "";
    }```

Should it be returned like this?

```private String overlapFrom(String segmentText) {
        if (maxOverlapSize == 0) {
            return "";
        }

        SegmentBuilder overlapBuilder = new SegmentBuilder(maxOverlapSize, this::sizeOf, joinDelimiter());

        String[] sentences = new DocumentBySentenceSplitter(1, 0, null, null).split(segmentText);
        for (int i = sentences.length - 1; i >= 0; i--) {
            String part = sentences[i];
            if (overlapBuilder.hasSpaceFor(part)) {
                overlapBuilder.prepend(part);
            } else {
                return overlapBuilder.build();
            }
        }

        **return return overlapBuilder.build();**
    }```

- LangChain4j version: e.g. 0.24.0

[xbzhang1994]

I'm not sure if this is correct, but it can satisfy my understanding of the maxOverlapSize parameter.

[langchain4j]

@18856317221 thank you for reporting! It is indeed a bug, here is a fix: #464