//  FileCompare.java  Copyright (c) 2006 Kari Laitinen

//  http://www.naturalprogramming.com

//  2006-02-21   File created.
//  2006-02-21   Last modification.

//  A solution to Exercise 14-6.

import java.util.* ;
import java.io.* ;  // Classes for file handling.

class FileCompare
{
   public static void main( String[]  command_line_parameters  )
   {
      Scanner keyboard =  new Scanner( System.in ) ;

      String  name_of_first_file ;
      String  name_of_second_file ;

      if ( command_line_parameters.length  ==  2 )
      {
         name_of_first_file  =  command_line_parameters[ 0 ] ;
         name_of_second_file =  command_line_parameters[ 1 ] ;
      }
      else
      {
         System.out.print( "\n This program compares a file"
                         + "\n to another file. Please, give the name of"
                         + "\n the first file: " ) ;

         name_of_first_file  =  keyboard.nextLine() ;

         System.out.print( "\n Give the name of the second file: " ) ;

         name_of_second_file  =  keyboard.nextLine() ;
      }

      try
      {
         FileInputStream first_file  =
                          new FileInputStream( name_of_first_file ) ;

         FileInputStream second_file  =
                          new FileInputStream( name_of_second_file ) ;

         System.out.print( "\n Comparison in progress ... \n" ) ;

         int  number_of_bytes_compared  =  0 ;

         //  If this program were used for serious file comparison
         //  operations, it might be better to use a larger array
         //  (input buffer) into which bytes are read.

         byte[]  bytes_from_first_file  =  new  byte[ 128 ] ;
         byte[]  bytes_from_second_file  =  new  byte[ 128 ] ;

         boolean  files_are_equal      =  true  ;
         boolean  comparison_is_ready  =  false ;

         while ( files_are_equal  ==  true  &&
                 comparison_is_ready  ==  false )
         {
            int  first_number_of_bytes  =
                               first_file.read( bytes_from_first_file ) ;
            int  second_number_of_bytes  =
                               second_file.read( bytes_from_second_file ) ;

            // The following line was used when this program was tested.

            // System.out.print( " " + first_number_of_bytes + " " 
            //                +  second_number_of_bytes ) ;

            //  Method read() returns -1 when there is no more data because
            //  the end of file has been encountered.

            if ( first_number_of_bytes  ==  -1  &&
                 second_number_of_bytes  ==  -1 )
            {
               comparison_is_ready  =  true ;
            }
            else if ( first_number_of_bytes  !=  second_number_of_bytes )
            {
               files_are_equal  =  false ;
            }
            else 
            {
               int byte_index  =  0 ;

               while (  byte_index  <  first_number_of_bytes  &&
                        files_are_equal  ==  true  )
               {
                  if ( bytes_from_first_file[ byte_index ]  !=
                                  bytes_from_second_file[ byte_index ] )
                  {
                     files_are_equal  =  false ;
                  }

                  number_of_bytes_compared  ++  ;
                  byte_index  ++ ;
               }
            }
         }

         if ( files_are_equal  ==  true )
         {
            System.out.print( "\n The files are equal. " ) ;
         }
         else
         {
            System.out.print( "\n The files are NOT equal. " ) ;
         }

         System.out.print( "\n  "  +  number_of_bytes_compared
                      + "  bytes were compared. \n" ) ;

         first_file.close() ;
         second_file.close() ;
      }
      catch ( FileNotFoundException  caught_file_not_found_exception )
      {
         System.out.print( "\n Cannot open both files " ) ;
      }
      catch ( IOException  caught_io_exception )
      {
         System.out.print( "\n Error while processing the files " ) ;
      }
   }
}