Should I explain that all threads are closed if they are wrapped in a buffer through 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(); } } 

Today I came across this question and am not sure whether they will be closed, since they are wrapped or it is still necessary to close all threads independently of each other.

Answer 1

If any reader or stream decorates another reader / stream, then closing the outside also closes the inside. This can be done from the Javadoc Closeable#close() :

Closes this thread and allocates any associated system resources .

This also applies to core resources.

If you are very curious, you can delve into the sources of these classes, for example. 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 base Reader .

Answer 2

Yes, decorated streams are also closed.

 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 a try-with-resource block (and the fact that closing the reader closes the rest)

 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); }