nhaarman nhaarman - 1 month ago 13
Java Question

Does closing a Stream close the BufferedReader source?

From the docs:


Streams have a BaseStream.close() method and implement AutoCloseable,
but nearly all stream instances do not actually need to be closed
after use. Generally, only streams whose source is an IO channel (such
as those returned by Files.lines(Path, Charset)) will require closing.
Most streams are backed by collections, arrays, or generating
functions, which require no special resource management. (If a stream
does require closing, it can be declared as a resource in a
try-with-resources statement.)


When I create a
Stream<String>
using the
lines()
method on a
BufferedReader
as seen below, does closing the
Stream
also close the
BufferedReader
?

try (Stream<String> lines = new BufferedReader(new InputStreamReader(process.getInputStream())).lines()) {
// Do stuff
}

// Is the BufferedReader, InputStreamReader and InputStream closed?


Some really quick tests I've tried say no (the
in
field of the
BufferedReader
is not
null
), but then I'm confused by the following sentence, since this example is I/O as well, right?


Generally, only streams whose source is an IO channel (such
as those returned by Files.lines(Path, Charset)) will require closing.


If not, do I need to close both instances, or will closing the
BufferedReader
suffice?




Ideally, I'd like to return a
Stream<String>
from some method, without having the client worry about the readers. At the moment, I've created a
Stream
decorator which also closes the reader, but it's easier if that isn't necessary.

Answer Source

No, seems it doesn't. As the stream is created using

    return StreamSupport.stream(Spliterators.spliteratorUnknownSize(
            iter, Spliterator.ORDERED | Spliterator.NONNULL), false);

which doesn't pass any reference to the the BufferedReader