A good answer might be:

The blanks are filled below.

Using the ! operator with the exists() method tests that a file (or a directory) does exist.

import java.io.*;
class CopyBytes
{
  public static void main ( String[] args ) 
  {
    DataInputStream  instr;
    DataOutputStream outstr;

    if ( args.length != 3 || !args[1].toUpperCase().equals("TO") )
    {
      System.out.println("java CopyBytes source to destination");
      return;
    }

    File inFile  = new File( args[0] );
    File outFile = new File( args[2] );

    if ( outFile.exists() )
    {
      System.out.println( args[2] + " already exists");
      return;
    }

    if ( ! inFile.exists() )
    {
      System.out.println( args[0] + " does not exist");
      return;
    }

    .  .  .  .  

   }
}

The rest of the program could remain unchanged without any problem, but now that the two File objects have been constructed and tested it would be nice to continue using them.

QUESTION 7:

Review:

• What stream type is used with a byte-oriented input file?
• What stream type is used with a byte-oriented output file?