Ed's lab

import java.io.*;
import java.util.*;

public class EraseObject 
{
	final static int MAXCOL=20;
	final static int MAXROW=20;
	final static char BLANK=' ';
	public static void main (String []args)throws IOException
	{
		int x=0;
		int y=0;
		Scanner s=new Scanner(System.in);
		String sentinel="y";
		EraseObject object=new EraseObject();
		char[][]matrix=new char[MAXROW+1][MAXCOL+1];
		
		object.loadMatrix(matrix);
		object.printMatrix(matrix);
		
		while (sentinel.equals("y")||sentinel.equals("Y"))
		{
			System.out.print("Enter a row\t");
			x=s.nextInt();
			System.out.print("Enter a column\t");
			y=s.nextInt();

			object.erase(matrix,x,y);
			object.printMatrix(matrix);
			
			System.out.println("Do you want to continue?");
			sentinel=s.next();
				
		}
		
			
	}
	
	public  void printMatrix(char [][]matrix)throws IOException
	{
		PrintWriter outfile=new PrintWriter(new FileWriter("outData.dat",true));
		System.out.println("  12345678901234567890");
		for (int row=1;row<=20;row++)
		{
			System.out.print(row%10+" ");
			for (int col=1;col<=20;col++)
			{
				outfile.print(""+matrix[row][col]);
				System.out.print(""+matrix[row][col]);
			}
			System.out.println();
			outfile.println();
		}
		System.out.println();
		outfile.println();
		outfile.close();
	}
	
	public void loadMatrix(char[][]matrix) throws IOException
	{
		int x=0;
		int y=0;
		try
		{	
			FileReader reader=new FileReader("digital.txt");
			Scanner sf=new Scanner(reader);
			int numPairs=sf.nextInt();
			for (int row=0;row<=20;row++)
			{
				for (int col=0;col<=20;col++)
				{
					matrix[row][col]='-';
				}
			}
			for (int i=0;i<numPairs;i++)
			{
				x=sf.nextInt();
				y=sf.nextInt();
				matrix[x][y]='@';
			}
			sf.close();
		}
		
		catch (IOException e)
		{
			System.out.println("File problem");
		}
		
	}
	
	public void erase(char[][] matrix,int x, int y)
	{
		if (1<=x&&x<=MAXROW&&1<=y&&y<=MAXCOL)
		{	
			if (matrix[x][y]=='@')
			{
				matrix[x][y]='-';
				erase(matrix,x-1,y);
				erase(matrix,x+1,y);
				erase(matrix,x,y+1);
				erase(matrix,x,y-1);
			}
		}
		
	}		
		
	
}