Copy a file - Real's Java How-to

Copy a fileTag(s): IO

[Old technique (pre JDK1.4)]

import java.io.*;

public class FileUtils{
  public static void copyFile(File in, File out) throws Exception {
    FileInputStream fis  = new FileInputStream(in);
    FileOutputStream fos = new FileOutputStream(out);
    try {
        byte[] buf = new byte[1024];
        int i = 0;
        while ((i = fis.read(buf)) != -1) {
            fos.write(buf, 0, i);
        }
    } 
    catch (Exception e) {
        throw e;
    }
    finally {
        if (fis != null) fis.close();
        if (fos != null) fos.close();
    }
  }
  
  public static void main(String args[]) throws Exception{
    FileUtils.copyFile(new File(args[0]),new File(args[1]));
  }
}

[JDK1.4 using the java.nio package (faster)]

import java.io.*;
import java.nio.channels.*;

public class FileUtils{
    public static void copyFile(File in, File out) 
        throws IOException 
    {
        FileChannel inChannel = new
            FileInputStream(in).getChannel();
        FileChannel outChannel = new
            FileOutputStream(out).getChannel();
        try {
            inChannel.transferTo(0, inChannel.size(),
                    outChannel);
        } 
        catch (IOException e) {
            throw e;
        }
        finally {
            if (inChannel != null) inChannel.close();
            if (outChannel != null) outChannel.close();
        }
    }

    public static void main(String args[]) throws IOException{
        FileUtils.copyFile(new File(args[0]),new File(args[1]));
  }
}

NOTE:
In win2000 , the transferTo() does not transfer files > than 2^31-1 bytes. it throws an exception of "java.io.IOException: The parameter is incorrect"
In solaris8 , Bytes transfered to Target channel are 2^31-1 even if the source channel file is greater than 2^31-1
In LinuxRH7.1 , it gives an error of java.io.IOException: Input/output error

ref : http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=4643189

On the Windows plateform, you can't copy a file bigger than 64Mb, an Exception in thread "main" java.io.IOException: Insufficient system resources exist to complete the requested service is thrown.

For a discussion about this see : http://forum.java.sun.com/thread.jspa?threadID=439695&messageID=2917510

The workaround is to copy in a loop 64Mb each time until there is no more data.

Replace

        ...
        try {
            inChannel.transferTo(0, inChannel.size(),
                    outChannel);
        } 
        ...

        ...
        try {
           // magic number for Windows, 64Mb - 32Kb)
           int maxCount = (64 * 1024 * 1024) - (32 * 1024);
           long size = inChannel.size();
           long position = 0;
           while (position < size) {
              position += 
                inChannel.transferTo(position, maxCount, outChannel);
        } 
        ...