Do I have to explicity close all streams, if they're wrapped in a buffer via java?

Question

private InputStream input;
private InputStreamReader inputReader;
private BufferedReader reader;

try {
    input = new InputStream();
    inputStreamReader = new InputStreamReader(inputStream);
    reader = new BufferedReader(inputStreamReader);
    // do I/O operations
} catch (IOException e) {
    Log.d("IOException", "The Data Could Not Be Read =/");
} finally {
    try {
        reader.close(); // now will this, by default, close all other streams? OR
      /*
       * input.close(); inputStream.close(); //is this necessary, along with
       * reader.close();
       */
    } catch (IOException ex) {
        ex.printStackTrace();
    }
}

I came across this question today, and am not sure whether they'll be closed, since it's wrapped, or if it is still necessary to close all streams independently.

Answer 1

If any reader or stream decorates another reader/stream, then closing the outer one also closes the inner. This can be implied from the Javadoc of Closeable#close():

Closes this stream and releases any system resources associated with it.

That applies to the underlying resources, too.

If you're very curious you can dig into the sources of those classes, eg. in BufferedReader:

public void close() throws IOException {
    synchronized (lock) {
        if (in == null)
            return;
        try {
            in.close();
        } finally {
            in = null;
            cb = null;
        }
    }
}

where in is the underlying Reader.

Answer 2

Yes, decorated streams are closed too.

InputStream in = new FileInputStream("c:\\myfile.txt");
InputStreamReader reader = new InputStreamReader(in);
BufferedReader bufferedReader = new BufferedReader(reader);

bufferedReader.close();

in.read(); // throws an IOException (no such file or directory)
reader.read(); // throws an IOException (Stream closed)

Answer 3

From Java 7 you can use the try-with-resource block (and the fact that closing reader closes the others)

try (BufferedReader reader = new BufferedReader(
                              new InputStreamReader(new FileInputStream(file), "UTF-8"))) {

    // do I/O operations
} catch(IOException e) {
    Log.d("IOException", "The Data Could Not Be Read =/", e);
}