Java/Language Basics/finally

Close stream in finally

 
/*
 * 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) {
      }
    }
  }
}

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

/*
 * 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!");
    }
  }
}