Enterting File to be used at the command line (help!)

Question

I have this code which works on by loading a .txt which hold a matrix of numbers and doing some maths and the like on it. the problem with this is that it is limited to only being able to read from that one file. i would like to make it possible to enter the name of the .txt file at the command line when running the program
e.g java FlatCost costs.txt
heres the code so far (it works).
import java.io.*;
import java.util.Vector;
public class FlatCost
    public static void main(String[] args) throws IOException    {       
        FileInputStream stream = new FileInputStream("costs.txt");
        InputStreamReader reader = new InputStreamReader(stream);       
        StreamTokenizer tokens = new StreamTokenizer(reader);       
        Vector v = new Vector();
        while(tokens.nextToken() != tokens.TT_EOF)        {           
            v.add(new Integer((int) tokens.nval));
            System.out.println(new Integer((int) tokens.nval));        }       
        System.out.println("Enter floor number: ");       
        BufferedReader in = new BufferedReader(new InputStreamReader(System.in));
        String line1 = in.readLine();
        int x = Integer.parseInt(line1);
        if(x > 3) System.out.println("Sorry, out of range");
        System.out.println("Enter no. rooms: ");       
        String line2 = in.readLine();          
        int y = Integer.parseInt(line2);
        if(y > 2) System.out.println("Sorry, out of range");
        int numFloors = v.size()/4;               
        int dest = ((x*4) + y + 1);
        System.out.println("PRICE: " + v.get(dest));   
}Please help because i dont know how to do it
Carl

Answer 1

That's right... specificallyFileInputStream
stream = new FileInputStream(args[0]);
Also don't forget make sure the argument was supplied. Otherwise you'll get a runtime array out of bounds.
   if (args.length < 1) {
      System.out.println("Usage: java FlatCost filename");
      System.out.println("   eg: java FlatCost costs.txt");
      // exit or supply default file
   }