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Answer:

The blanks are filled, below.

Checking Command Line Arguments

Of course, you can use any names for the arguments of the catch{} clauses. The blocks have to be in the given order since FileNotFoundException is a child class of IOException Also, the blocks should actually do something.

try
{
    . . . . 
}
catch(  FileNotFoundException nfx  )
{
}

catch(  IOException iox  )
{
}

All that remains is to check the command line arguments. The command line looks like this:

java copyBytes sourceFile to destinationFile

Here is the part of the program that checks that the command line is correct:

public static void main ( String[] args ) 
{
  DataInputStream  instr;
  DataOutputStream outstr;
  
  if ( _________________ _____ _________________  )
  {
    System.out.println("java CopyBytes source to destination");
    return;
  }
  
  . . .

Sadly, there are three blanks which must be filled. Here is a list of possible blank-fillers:

QUESTION 20:

Fill the blanks. The error message is written out when the command line is incorrect.