Need help writing a toString

Question

I have no idea how to go about writing the toString method for this code. I have to print the array that provides the longest sequence. I would appreciate your help.
Here is the code: import java.io.FileReader;
import java.io.IOException;
import java.util.List;
import java.util.ArrayList;
import java.util.Scanner;
import java.util.StringTokenizer;
class Grid
    private int [ ][ ] mainGrid;
    public Grid( String file ) throws IOException
        FileReader fr = new FileReader( file );
        Scanner scan = new Scanner( fr );
        ArrayList<ArrayList<Integer>> numR = new ArrayList<ArrayList<Integer>>( );
        while( scan.hasNextLine( ) )
            String line = scan.nextLine( );
            StringTokenizer st = new StringTokenizer ( line );
            String number;
            ArrayList<Integer> numC = new ArrayList<Integer>( );
            while( st.hasMoreTokens( ) )
                number = st.nextToken( );
                int num = Integer.parseInt(number);
                numC.add(num);      
            numR.add( numC );
        int height = numR.size();
        int width = numR.get( 0 ).size();
        mainGrid = new int [height][width];
        for(int i = 0; i < height; i++)
            for( int j = 0; j < width; i++)
                mainGrid [ i ][ j ] = numR.get( i ).get( j );
    private class Position
        private int row;
        private int col;
        public Position( int r, int c )
            r = row;
            c = col;
        public List<Position> getAdjacents( )
            int lowRow = row != 0 ? row - 1 : 0;
            int lowCol = col != 0 ? col - 1 : 0;
            int highRow = row != mainGrid.length - 1 ? row + 1 : mainGrid.length - 1;
            int highCol = col != mainGrid[ 0 ].length - 1 ? col + 1 : mainGrid[ 0 ].length - 1;
            List<Position> result = new ArrayList<Position>( );
            for( int r = lowRow; r <= highRow; r++ )
                for( int c = lowCol; c <= highCol; c++ )
                    if( r != row || c != col )
                        result.add( new Position( r, c ) );
            return result;
        public boolean equals( Object other )
            if( ! ( other instanceof Position ) )
                return false;
            Position rhs = (Position) other;
            return row == rhs.row && col == rhs.col;
        public int getValue( )
            return mainGrid [ row ][ col ];
        public String toString( )
            return "(" + row + "," + col + ")";
    public Position newPosition( int r , int c )
        return new Position( r, c );
    // Public driver
    public List<Position> getSequence( )
         List<Position> sequence = new ArrayList<Position>( );
         for( int r = 0; r < mainGrid.length - 1; r++)
              for( int c = 0; c < mainGrid[ 0 ].length - 1; c++)
                   sequence = getSequence( new Position( r, c ));          
         return sequence;
    // Recursive routine
    private List<Position> getSequence( Position pos )
      List<Position> adj = pos.getAdjacents( );
      if( adj.size( ) == 0)
           List<Position> seq = new ArrayList<Position>( );
           seq.add( pos );
           return seq;
      List<Position> maxSeq = null;
      for( Position p: adj)
           List<Position> currentSeq = getSequence( p );
           if( currentSeq.size( ) < maxSeq.size( ))
                maxSeq = currentSeq;
      maxSeq.add( pos );
      return maxSeq;
    public String toString( )
         StringBuffer sb = new StringBuffer( );
          return new String( sb );
class MaxSubsequence
    public static void main( String [ ] args )
        try
             System.out.println( new Grid( "numbergrid1.txt" ));
        catch( IOException e)
             System.err.println( "Error opening file");
}

Answer 1

Call your getSequence method from the toString
method. This gives you a List. Take a look at the
methods of List to see how you can iterate
over the list. Then look at the StringBuffer/Builder
class and see how you can add those elements (plus
any other formatting and words) to the final string.ok, i think i may be getting it a bit more. I don't need to use a loop at all?
I can just call the getSequence method, use a toArray to return the sequence and append the sequence to the new string?