Re: Understanding Exceptions

From:

Thomas Hawtin <usenet@tackline.plus.com>

Newsgroups:

comp.lang.java.help

Date:

Mon, 02 Oct 2006 15:05:47 +0100

Message-ID:

<45211c86$0$24473$ed2e19e4@ptn-nntp-reader04.plus.net>

candor wrote:

I'm trying to understand Exceptions and IO in Java and am faced with
the following small program which just copies one file to another.
The problem is that Eclipse tells me that I have two uncaught
Exceptions in the finally statement apparently originating from the
in.close() and out.close() statements.

Yes, (In|Out)putStream.close can throw exceptions. InputStream.close
throwing is highly unlikely in practice. In either case, an exception
thrown closing a stream is serious.

A better way to write the code is:

import java.io.*;

public class TestOfListOfNumbers {
     public static void main(String[] args) {
         try {
             FileInputStream in = new FileInputStream("d:\\xanadu.txt");
             try {
                 FileOutputStream out = new FileOutputStream("out.txt");
                 try {
                     int c;
                     while ((c=in.read()) != -1) { // INEFFICIENT
                          out.write(c);
                     }
                     // If you were to wrap in in a BufferedOutputStream,
                     // flush here.
                 } finally {
                     out.close();
                 }
             } finally {
                 in.close();
             }
         } catch (IOException e) {
             System.err.println("Caught IOException: " + e.getMessage());
         }
     }
}

Tom Hawtin