import java.util.Scanner; // bring in Scanner class so we can use it
import java.io.*;

public class Files
  /** This class Introduces Files **/
  // input files: program reads data from these files
  // output files: program will store data in these files
{
  public static void main(String[] args) throws IOException
  { 
    // Program can create an output file
    
    // create an object to represent a file on disk
    // this will delete the file if it previously exists
    PrintWriter outfile = new PrintWriter("data.txt");
    // this object can be used the same way you use System.out
    for (int i=1; i<10; i++)
        outfile.println(i);
    // when done, close the file
    outfile.close();
    
    // can use a String object to hold filename
    Scanner keyboard = new Scanner(System.in);
    System.out.println("What is the name of your output file?");
    String filename = keyboard.next();
    outfile = new PrintWriter(filename);
    
    outfile.println("Hello World!");
    outfile.close();
// READING IN DATA FROM A FILE        
    
    // First, create a File object that represents input file
    File myfile = new File("data.txt");
    /* Then, get a scanner object, but instead of connecting it to the
     * keyboard (System.in) I will connect it to a File object
     */
    Scanner infile = new Scanner(myfile);
    int num;
    for (int i=1; i<10; i++) {
      num = infile.nextInt();
      System.out.println("num in file is: " + num);
    }
    infile.close();
  }   
}