FileSystem diff INCOMPLETE

// 2012-08-16 johnpfeiffer requires FileSystem
// TODO: identification of one line difference in the middle (i.e. best guess line matching)
// TODO: buffering to provide large file size support


import java.io.IOException;
import java.util.ArrayList;


public class diff
{
    public static final String CORRECTUSAGE = "java -jar diff filename1 filename2";
    private ArrayList <String> firstFileAsArrayList;
    private ArrayList <String> secondFileAsArrayList;
    private StringBuilder result;

    public static void main( String[] args )
    {
        if( args.length != 2 )
        {
            System.err.println( CORRECTUSAGE );
            System.exit( 1 );
        }

        FileSystem fs = new FileSystem();
        String firstFileName = args[0];
        String secondFileName = args[1];


        diff main = new diff();
        main.result = new StringBuilder();
        try{
            main.firstFileAsArrayList = fs.listOfLinesFromFile( firstFileName );
            main.secondFileAsArrayList = fs.listOfLinesFromFile( secondFileName );
            long firstLineCount = main.firstFileAsArrayList.size();
            long secondLineCount = main.secondFileAsArrayList.size();
            if( firstLineCount != secondLineCount )
            {
                main.result.append( "Files do not match: " + firstLineCount + " != " + secondLineCount );
            }

            //TODO: currently exits on first non match
            int counter = 0;
            StringBuilder correspondingLine = new StringBuilder();
            for( String line : main.firstFileAsArrayList )
            {

                = main.secondFileAsArrayList.get( counter );
                if( !line.equals( correspondingLine  ) )
                {
                    main.result.append( "line number " + counter + " does not match" );
                    main.result.append( line );
                    main.result.append( line );

                }
                counter++;

            }
        }catch( IOException e )
        {
            main.result.append( "ERROR: " + e + " : " + CORRECTUSAGE );
        }catch( IllegalArgumentException e )
        {
            main.result.append( "ERROR: " + e + " : " + CORRECTUSAGE );
        }


    }

    private void cleanShutdown()
    {
        System.out.println( result.toString() );

    }
} //end class