/*
   This program takes two file names from the command line
   and copies the first text file to the second.  It is an
   example showing how to open, close, read and write text
   files.
*/

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

public class Copy
{
   
   public static void main(String[] args)
   {
      Scanner in;
      BufferedWriter out;
      // check for valid command line
      if (args.length != 2)
      {
         System.out.println("Usage: java Copy inputfilename outputfilename");
         System.exit(1);
      }
      // open input and output files
      in = openInput(args[0]);
      if (in == null)
         System.exit(1);
      out = openOutput(args[1]);
      if (out == null)
         System.exit(1);
      // all file operations must be inside try/catch blocks
      try
      {
         while (in.hasNext())
         {
            String textLine = in.nextLine();    // read a line
            out.write(textLine);                // write the line
            out.newLine();
         }
         out.close();     // if this is left out some output may not be written
      }
      catch (IOException e)
      {
         System.out.println("file operation failed");
      }
   }
   
   // opens file named s for reading -- returns null if fails
   private static Scanner openInput(String s)
   {
      Scanner in;
      // all file operations must be inside try/catch blocks
      try
      {
         FileReader fr = new FileReader(s);   
         // open the file
         /* BufferedReader can be skipped and fr
            passed to the Scanner constructor.  Using
            a BuffredReader improves efficiency.
         */
         BufferedReader br = new BufferedReader(fr);
         /* Using a Scanner allows "ordinary" reading from
            tge file similar to reading from the keyboard.
         */
         in = new Scanner(br);
      }
      catch (IOException e)
      {
         System.out.println("Unable to open " + s);
         return null;
      }
      return in;
   }
   
   // opens file named s for wtiting -- returns null if fails
   private static BufferedWriter openOutput(String s)
   {
      BufferedWriter out;
      // all file operations must be inside try/catch blocks
      try
      {
         FileWriter fw = new FileWriter(s);    //open the file
         /* BufferedWriter can be skipped.  Using
            a BuffredWriter improves efficiency.
         */
         out = new BufferedWriter(fw);
      }
      catch (IOException e)
      {
         System.out.println("Unable to open " + s);
         return null;
      }
      return out;
   }
      
}