question: private static long copy ( InputStream source , OutputStream sink ) throws IOException { long nread = 0L ; byte [ ] buf = new byte [ BUFFER_SIZE ] ; int n ; while ( ( n = source . read ( buf ) ) > 0 ) { sink . write ( buf , 0 , n ) ; nread += n ; } return nread ; }
target:  Reads all bytes from an input stream and writes them to an output stream.