Java/Language Basics/finally

Close stream in finally

   <source lang="java">

/*

* Copyright (c) 2004 David Flanagan.  All rights reserved.
* This code is from the book Java Examples in a Nutshell, 3nd Edition.
* It is provided AS-IS, WITHOUT ANY WARRANTY either expressed or implied.
* You may study, use, and modify it for any non-commercial purpose,
* including teaching and use in open-source projects.
* You may distribute it non-commercially as long as you retain this notice.
* For a commercial use license, or to purchase the book, 
* please visit http://www.davidflanagan.ru/javaexamples3.
*/

//package je3.nio; import java.io.FileInputStream; import java.io.FileOutputStream; import java.io.IOException; import java.nio.channels.Channels; import java.nio.channels.FileChannel; import java.nio.channels.WritableByteChannel; /**

* FileCopy2.java: this program copies the file named in its first argument to
* the file named in its second argument, or to standard output if there is no
* second argument.
*/

public class FileCopy2 {

 public static void main(String[] args) {
   FileInputStream fin = null; // Streams to the two files.
   FileOutputStream fout = null; // These are closed in the finally block.
   try {
     // Open a stream to for the input file and get a channel from it
     fin = new FileInputStream(args[0]);
     FileChannel in = fin.getChannel();
     // Now get the output channel
     WritableByteChannel out;
     if (args.length > 1) { // If there is a second filename
       fout = new FileOutputStream(args[1]); // open file stream
       out = fout.getChannel(); // get its channel
     } else { // There is no destination filename
       out = Channels.newChannel(System.out); // wrap stdout stream
     }
     // Query the size of the input file
     long numbytes = in.size();
     // Bulk-transfer all bytes from one channel to the other.
     // This is a special feature of FileChannel channels.
     // See also FileChannel.transferFrom()
     in.transferTo(0, numbytes, out);
   } catch (IOException e) {
     // IOExceptions usually have useful informative messages.
     // Display the message if anything goes wrong.
     System.out.println(e);
   } finally {
     // Always close input and output streams. Doing this closes
     // the channels associated with them as well.
     try {
       if (fin != null)
         fin.close();
       if (fout != null)
         fout.close();
     } catch (IOException e) {
     }
   }
 }

}

</source>
   
  
 
  

Test case for finally, to show its effect with return or exit

   <source lang="java">

/*

* Copyright (c) Ian F. Darwin, http://www.darwinsys.ru/, 1996-2002.
* All rights reserved. Software written by Ian F. Darwin and others.
* $Id: LICENSE,v 1.8 2004/02/09 03:33:38 ian Exp $
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
*    notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
*    notice, this list of conditions and the following disclaimer in the
*    documentation and/or other materials provided with the distribution.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS""
* AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
* TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
* PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS
* BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
* CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
* SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
* INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
* CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
* ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
* POSSIBILITY OF SUCH DAMAGE.
* 
* Java, the Duke mascot, and all variants of Sun"s Java "steaming coffee
* cup" logo are trademarks of Sun Microsystems. Sun"s, and James Gosling"s,
* pioneering role in inventing and promulgating (and standardizing) the Java 
* language and environment is gratefully acknowledged.
* 
* The pioneering role of Dennis Ritchie and Bjarne Stroustrup, of AT&T, for
* inventing predecessor languages C and C++ is also gratefully acknowledged.
*/

/** Test case for "finally", to show its effect with

* return or exit.
*/

public class Finally {

 /** Main method, does the work of the testing... */
 public static void main(String[] argv) {
   try {
     throw new Exception();
   } catch (Exception e) {
     System.out.println("Caught Exception");
     return;    // with return, Goodbye appears
     // System.exit(1);  // with exit, Goodbye does not appear
   } finally {
     System.out.println("Goodbye!");
   }
 }

}

      </source>