Question 1

How does Fastexcel compare to Apache POI for large Excel files?

Accepted Answer

Fastexcel is significantly faster and uses less memory than Apache POI, with benchmarks showing up to 10x speed improvements and 12x lower heap usage. However, it has fewer features, so it's better for performance-critical tasks without advanced Excel needs.

Question 2

Can Fastexcel read Excel files with charts and graphs?

Accepted Answer

No, Fastexcel does not support reading or writing charts and graphs. It focuses on cell data, basic styles, and formatting, so for graphical elements, you need to use a full-featured library like Apache POI.

Question 3

How to generate an Excel file with multiple sheets using threads in Java?

Accepted Answer

Use Fastexcel's multithreaded generation: create a Workbook, add worksheets, and use CompletableFuture to fill each sheet concurrently in separate threads, as shown in the README example with runAsync calls.

Question 4

Does Fastexcel support formulas in Excel cells?

Accepted Answer

Yes, you can add formulas using the ws.formula(row, col, formula) method. Note that formulas are written as-is without evaluation, so cell values must be set separately if needed for display.

Question 5

How to read a massive Excel file without running out of memory?

Accepted Answer

Use Fastexcel's streaming reader: open a ReadableWorkbook, get the sheet, and use openStream() to process rows incrementally, discarding styles for efficiency, which prevents loading the entire file into memory.

Question 6

Is Fastexcel or Excel Streaming Reader better for reading large xlsx files?

Accepted Answer

Fastexcel's reader is about 2x faster than Apache POI's streaming API and simpler to use, but if you need to preserve styles or use features like Excel Streaming Reader's compatibility, Apache POI might be more suitable despite the performance trade-off.

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