Testing that a File 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;
    }

    .  .  .  .  

   }
}