How to simplify/reuse this exception handling code

Question

I tend to write code like the following a lot:

BufferedWriter w = null; // Or any other object that throws exceptions and needs to be closed
try {
    w = new BufferedWriter(new FileWriter(file));
    // Do something with w
} catch (IOException e) {
    e.printStackTrace();
} finally {
    if (w != null) {
        try {
            w.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

It usually involves an object that throws exceptions and needs to be closed, and that closing it may also throw an exception.

I was wondering if the above code can be simplified or reused in any way.

Answer 1

If you don't want to write code for closing in finally block, you should have a look at Project Lombok

Instead of writing the normal

public class CleanupExample {
  public static void main(String[] args) throws IOException {
  InputStream in = new FileInputStream(args[0]);
  try {
    OutputStream out = new FileOutputStream(args[1]);
    try {
      byte[] b = new byte[10000];
      while (true) {
         int r = in.read(b);
         if (r == -1) break;
         out.write(b, 0, r);
      }
    } finally {
        out.close();
      }
  } finally {
     in.close();
    }
  }
}

With Lombok you can write

public class CleanupExample {
  public static void main(String[] args) throws IOException {
    @Cleanup InputStream in = new FileInputStream(args[0]);
    @Cleanup OutputStream out = new FileOutputStream(args[1]);
    byte[] b = new byte[10000];
    while (true) {
      int r = in.read(b);
      if (r == -1) break;
      out.write(b, 0, r);
    }
   }
 }

Much more readable, and it generates the correct way of closing the Stream. This works with all the Closeable interfaces

Answer 2

I usually put contents of your finally block in a helper. Like this

void close(Closeable c) {
    if (c != null) {
        try {
            c.close();
        } catch (IOException e) {
            // perform logging or just ignore error
        }
    }
}

Closeable interface is implemented by many classes (input streams, database connections, etc), so this is kinda general-purpose helper.