Determine the source -- BufferedReader

Question

I have start Java programming and one of the function that I need to make is a read(), which accept PrintStream and BufferedReader. In this function, it supposes to determine whether the BufferedReader is from a keyboard (system.in) or a file. Now, I wonder how do you know if BufferedReader is accepting a keyboard or a file?
public static void main (String [] args) throws Exception
BufferedReader kb = new BufferedReader(new InputStreamReader(System.in));
System.out.print("\nPlease enter a file name with extension: ");
String inFileName = kb.readLine();
BufferedReader br = new BufferedReader(
new InputStreamReader(
new FileInputStream(
     new File(inFileName))));
//Obviously I could send either one... kb or br;
Fraction.read(System.out, kb); //accept user input and print on monitor
Fraction.read(System.out, br); //accept file input and print on monitor
public static Fraction read(PrintStream ps, BufferedReader br) throws Exception
//What do I need to test whether br == file or keyboard?

Answer 1

Your code doesn't make much sense, though... why would you ever want to pass 'kb' to Fraction.read()? So that you can get use input rather than reading it from a file? That's all well and good, but your problem isn't determining the BufferedReader source, it's in distinguishing whether the user wants to use the keyboard or a file. Another odd thing about your code is that, there really isn't any reason to know the source of the BufferedReader data at all... whether you pass kb or br, the way you read stuff will be the same.
Try something more like:
1) Ask user for a file name.
2) If user doesn't enter a file name, then tell them to type whatever data they wan't processed and pass kb to Fraction.read().
3) If user does enter a file name, the pass br to Fraction.read().