To copy a file in …

... Java

private static void copyFile(File srcFile, File destFile) 
       throws IOException {
   FileInputStream is = null;
   FileOutputStream os = null;
   try {
       is = new FileInputStream(srcFile);
       FileChannel iChannel = is.getChannel();
       os = new FileOutputStream( destFile, false );
       FileChannel oChannel = os.getChannel();
       oChannel.transferFrom( iChannel, 0, srcFile.length() );
   }
   finally {
       if (is != null) is.close();
       if (os != null) os.close();
   }
}

... Groovy

static void copyFile(File source, File destination) {
   def reader = source.newReader()
   destination.withWriter { writer ->
       writer << reader
   }
   reader.close()
}

... Groovy with a salt of Ant

static void copyFile(File source, File destination) {
   new AntBuilder().copy(file:'$source.canonicalPath', 
                         tofile:'$destination.canonicalPath')
}

... in shell

cp source destination