Should I close Streams created with java.nio.file.Files.newInputStream?

Question

In the stream tutorial, nothing is said about closing streams gained from Files.newInputStream( path ). Only some obscure:

Whether the returned stream is asynchronously closeable and/or interruptible is highly file system provider specific and therefore not specified.

What is "asyncronously" in this context? If I close the stream explicitly or if another thread closes the stream asyncronously?

Brabble

Left unclosed, it seems to keep a file descriptor occupied per file provided by the stream... which is really not what you may want dealing with large directories. – Shanonshanta

Answer 1

You definitely must close the obtained InputStream, just like all others. The term "asynchronously closeable" refers to the ability to close the stream while another thread is blocked on an I/O operation on it.

From InterruptibleChannel documentation:

A channel that implements this interface is asynchronously closeable: If a thread is blocked in an I/O operation on an interruptible channel then another thread may invoke the channel's close method. This will cause the blocked thread to receive an AsynchronousCloseException.

Olivaolivaceous

So the authors of the tutorial just forgot about closing the streams? docs.oracle.com/javase/tutorial/essential/io/… – Brabble

No. They use the proper Automatic Resource Management idiom. – Olivaolivaceous

That is what I want to know, what is this Idiom where is it described? Is the destructor closing the stream? I seem to have overlooked an essential part. – Brabble

Found it, here: oracle.com/technetwork/articles/java/… Thank you so much! – Brabble

Answer 2

You can do this conveniently with the new try with resources option.

try(/*initialize resources here*/)
{
}

They will automatically be closed after the try block. Add a catch as necessary.

Gawk