Reading from a file. How to ask the user for file name at run time????

Question

I have the code to read from a file but my problem is how to prompt the user for the file name at run time.
import java.io.File;
import java.io.FileNotFoundException;
import java.util.InputMismatchException;
import java.util.Scanner;
public class FileRead {
    public static void main(String args[]) {
        Scanner scan = null;
        File file = new File("Results.txt");
        String number;
        try {
            scan = new Scanner(file);
            while (scan.hasNext()){
            number = scan.next();
            System.out.println(number);}
        catch (FileNotFoundException ex1){
            System.out.println("No such file");
        catch (IllegalStateException ex2){
            System.out.println("Did you close the read by mistake");
        catch (InputMismatchException ex){
            System.out.println("File structure incorrect");
        finally{
            scan.close();}
}Any hints would be greatly appreciated. Thank you in advance

Answer 1

I have read through some of the tutorials that you have directed me too and they are very useful, thank you. however there are still a few things that i am not clear about. I am using net beans 5.0 I have placed a text file named Results.txt into the project at the root so the program can view it.
When I use the code that you provided me with, does it matter where the file is, or will it look through everywhere on the hard drive to find a match?
This code compiles but at run time it comes up with this error
run-single:
java.lang.NoClassDefFoundError: NamedFile
Exception in thread "main"
Java Result: 1
BUILD SUCCESSFUL (total time: 3 seconds)
import java.util.Scanner;
import java.io.*;
class NamedFileInput
  public static void main (String[] args) throws IOException
    int num, square;   
    // this Scanner is used to read what the user enters
    Scanner user = new Scanner( System.in );
    String  fileName;
    System.out.print("File Name: ");
    fileName = user.nextLine().trim();
    File file = new File( fileName );     // create a File object
    // this Scanner is used to read from the file
    Scanner scan = new Scanner( file );     
    while( scan.hasNextInt() )   // is there more data to process?
      num = scan.nextInt();
      square = num * num ;     
      System.out.println("The square of " + num + " is " + square);
}his is the code that i used. It is the same as the code you posted for me (on chapter 23 I/O using Scanner and PrintStream) Sorry im just really stuck on this!!