CODEWITHSUNDEEP
javasocketsmemory-leaksstream
DonyorM
DonyorM

Reputation: 1800

Closing BufferedReader without closing wrapped stream

I'm currently writing a program that communicates with a server using TCP sockets. Part of that requires sending information back and forth through several methods. However, I do not want to open up a new socket connection for each request, but I can't guarantee the number or the order of the requests. In order to handle this, I simply keep one socket instance that gets reused a lot.

However, in order to read the data I use BufferedReader wrapper classes. Because I reuse the same socket, I can't call close() on the reader, or I'll close the socket stream as well.

Do I need to call close() on the BufferedReader if I don't want to close the underlying stream? Will I cause a memory leak by not doing this? If I do need to call close() how can I return the memory without closing the socket's stream?

Note: I will close the underlying stream at program termination, this question isn't about that.

Upvotes: 1

Views: 1688

Answers (1)

kdgregory
kdgregory

Reputation: 39606

Don't close the BufferedReade. More important, don't discard the BufferedReader; instead, pass it around rather than the SocketInputStream.

A BufferedReader, as its name implies, has an internal buffer. When you read from it, it tries to fill that buffer from the underlying Reader. Which means that, if you discard it, those bytes are gone.

And now some unasked advice:

  • Do you really want to use a Reader? Most communication protocols are better implemented using a DataInputStream/DataOutputStream. With a Reader you're limited to character data (and in the case of BR, lines of character data).
  • Are you paying attention to encoding? The correct way to construct a Reader on top of an InputStream is to use the two-argument variant of InputStreamReader: new InputStreamReader(in, "UTF-8") (you can use an encoding other than UTF-8, but have a good reason).
  • It's generally better to use a BufferedInputStream rather than a BufferedReader, because the translation from stream to reader may involve multiple reads. If you want readLine(), you can always use both.
  • Be sure to close the socket in either a finally or try-with-resources. See this for more info.

Upvotes: 3

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