When to close the InputStream object used in the constructor of HSSFWorkbook?

Question

I am working with HSSFWorkbook and I wanted to know where should I close the InputStream object that I have used while constructing the HSSFWorkbook object. Does HSSFWorkbook closes the stream in its constructor itself? or do we need to close it manually? And can we close it just after the constructor call? i.e., does HSSFWorkbook object use the InputStream object in its constructor only? or can it also use it in future (in this case we cant close it)? thank you.

public HSSFWorkbook loadSheet(File file) throws FileNotFoundException, IOException {
    return new HSSFWorkbook(new FileInputStream(file)); 
}

Answer 1

The constructor of HSSFWorkbook doesn't state whether the InputStream will be closed or left open, so at a first glance you shouldn't make assumptions that it's going to be closed. Digging deeper, however, the constructor of a class used within the constructor itself on the other hand does state clearly its behaviour.

At least in Apache POI 4.0.0 the call to new HSSFWorkbook(inputStream) will result in a call to new POIFSFileSystem(inputStream) which, in its implementation, does indeed appear to always close the stream and the constructor documentation confirms it.

This would seem to point to the following answers to your questions:

• Does HSSFWorkbook closes the stream in its constructor itself? Yes, indirectly.
• Or do we need to close it manually? Apparently not, unless they decide to no longer rely on POIFSFileSystem, which seems unlikely.
• And can we close it just after the constructor call? Apparently, yes... but there's no need for it.
• i.e. does HSSFWorkbook object use the InputStream object in its constructor only? Apparently so.