How do I avoid closing an InputStream passed to my method that I wrap in Reader streams?

Question

I'm creating a Java method that accepts a single InputStream as an argument. For the convenience of working with a character-based stream, I wrap the provided InputStream at the start of the method implementation as follows:

public void doStuff(InputStream inStream) {
   BufferedReader reader = new BufferedReader(new InputStreamReader(inStream));
   ...
}

Since the InputStream (inStream) is passed to my method, I don't want to close it ... as I think that should be the responsibility of the client calling my method (is this assumption correct?). However, I do think that I should close the BufferedReader that I created; but in doing so, I believe it will automatically close all the other composed streams including the inStream.

Does anyone see a way for me to close the BufferedReader and InputStreamReader that I created while not closing the InputStream passed to my method? Maybe there is a way to make a copy of the provided InputStream before I wrap it? Thanks

Answer 1

What I'd try would be overriding the close method:

BufferedReader reader = new BufferedReader(new InputStreamReader(inStream)){
    public void close() throws IOException {
        synchronized (lock) {
            if (in == null)
                return;
        }
    }
};
// rest of your code

Kind of crazy, but it should work. Though, I'm not sure this is the best approach.

I think this is an interesting question, so I hope someone expert gives his/her opinion.

Answer 2

Personally I would just avoid the problem by changing the signature of your method to require that a BufferedReader (or Reader) be passed in.

Answer 3

You do not need to close a BufferedReader or InputStreamReader or probably most reader implementations, when you do not wish to close the underlying reader.

These readers do not hold any resources that a call to close() would make free and which the garbage collector would not make free anyway (e.g. native resources or values in static variables) when you drop the reference to the reader at the end of your method.

The underlying input streams that communicate with native resources, e.g. FileInputStream or streams obtained from URLs, must be closed to free those native resources.

For Writer, there's a difference in that close() usually calls flush(). But then, you can call flush() directly.