copying files

[Csaba Kassitzky]

Hi everyone!

This might be a very noob question, but i still got problems with it:
How can i copy a file if the source and destination address is given?
Copying from line to line doesn't work on some files like pictures. How can i copy then?
Thanks!

[Rajagopal Manohar]

Originally posted by Csaba Kassitzky:
Copying from line to line doesn't work on some files like pictures. How can i copy then?
Thanks!

Looks like you are using the Readers and Writers of the IO API to do the copying

Using the Input/Output Stream's should do the trick in your case as the charecter encodings are preserved as is

Look at BufferedInputStream and BufferedOutputStream
That should help

-Rajagopal
[ December 07, 2005: Message edited by: Rajagopal Manohar ]

[Jesper de Jong]

See this:
The Java Developers Almanac - Copying One File to Another

[Csaba Kassitzky]

    try {
        // Create channel on the source
        FileChannel srcChannel = new FileInputStream("srcFilename").getChannel();
   
        // Create channel on the destination
        FileChannel dstChannel = new FileOutputStream("dstFilename").getChannel();
    
        // Copy file contents from source to destination
        dstChannel.transferFrom(srcChannel, 0, srcChannel.size());
    
        // Close the channels
        srcChannel.close();
        dstChannel.close();
    } catch (IOException e) {
    }

This seems nice, but what should i do, if my source is actually a web address(URL class)? I used this so far:

      URL url = new URL( whichOne );
      URLConnection urlConnection = url.openConnection( );
      BufferedReader in = new BufferedReader( new InputStreamReader( urlConnection.getInputStream( ) ) );
      BufferedWriter out = new BufferedWriter( new FileWriter( whereTo ) );
      String str;
      while( ( str = in.readLine( ) ) != null ) {
        out.write( str );
        out.newLine( );
      }
      in.close( );
      out.close( );

How can i modify this one?

[Jim Yingst]

If you're not using two files, then using the NIO classes here would get somewhat more complex. It's probably easier to stick to java.io classes instead. Rajagopal's post gave good advide for this. To copy files without modification, there's never any reason to use classes with Reader or Writer in their names. You want things that say InputStream and OutputStream. Here is an example that's close to what you want.

[Csaba Kassitzky]

This is good, but how do i put an URL into the sourcefile?

    void copy(String src, String dst) throws IOException {
        InputStream in = new FileInputStream(src);
        OutputStream out = new FileOutputStream(dst);
    
        // Transfer bytes from in to out
        byte[] buf = new byte[1024];
        int len;
        while ((len = in.read(buf)) > 0) {
            out.write(buf, 0, len);
        }
        in.close();
        out.close();
    }

This is what i have so far from it:

      URL url = new URL( src );
      URLConnection urlConnection = url.openConnection( );

[Paul Clapham]

You change your code so that it isn't expecting filenames as its parameters, and so that it can use things other than files. Perhaps like this:

void copy(InputStream src, OutputStream dst) throws IOException {
    
  // Transfer bytes from src to dst
  byte[] buf = new byte[1024];
  int len;
  while ((len = src.read(buf)) > 0) {
    dst.write(buf, 0, len);
  }
  // It's perhaps better to not close the streams here.
  // In general streams should be closed by the code that
  // created them. Also, if your code throws an IOException
  // then the close doesn't happen, so the caller would have
  // to close the streams anyway.
  src.close();
  dst.close();
}

Then to call that:

URL url = new URL( src );
  InputStream urlInput = url.Stream( );
  copy(urlInput, new FileOutputStream(fileName));

[Csaba Kassitzky]

Thanks for the help!
They seem to work now.