Re: different try-finally approach

According to Pitch <mail@fake.info>:


There might be a confusion with a third pattern which looks like this:

// =====================================================================

public static int readFromFile(String name, byte[] buf, int off, int len)
    throws MyException
{
    InputStream in = null;
    try {
        in = new FileInputStream(name);
        int orig = off;
        while (len > 0) {
            int rlen = in.read(buf, off, len);
            if (rlen < 0)
                break;
            off += rlen;
            len -= rlen;
        }
        return off - orig;
    } catch (IOException ioe) {
        throw new MyException(ioe);
    } finally {
        if (in != null) {
            try {
                in.close();
            } catch (IOException ioe) {
                // ignored
            }
        }
    }
}

// =====================================================================

The method above reads some bytes from a file. It is defined to throw a
custom exception (MyException) but _not_ a raw IOException. Since the
creation of a FileInputStream instance may throw such an exception, it
has to occur within the 'try' block, hence the use of the initialization
to 'null'.

The code above could be rewritten with a nested block:

// =====================================================================

public static int readFromFile(String name, byte[] buf, int off, int len)
    throws MyException
{
    try {
        InputStream in = new FileInputStream(name);
        try {
            int orig = off;
            while (len > 0) {
                int rlen = in.read(buf, off, len);
                if (rlen < 0)
                    break;
                off += rlen;
                len -= rlen;
            }
            return off - orig;
        } finally {
            in.close();
        }
    } catch (IOException ioe) {
        throw new MyException(ioe);
    }
}

// =====================================================================

However, that version does not perform _exactly_ the same thing (in case
the close() call throws an exception), and whether it is prettier than
the previous is, at best, arguable.

    --Thomas Pornin