Re: Stuck in while loop prison.

From:

Knute Johnson <nospam@rabbitbrush.frazmtn.com>

Newsgroups:

comp.lang.java.help

Date:

Sun, 04 Feb 2007 21:48:05 -0800

Message-ID:

<pyzxh.285267$fh6.234083@newsfe13.lga>

mmoski wrote:

Hmm... it should be just... enter the input, hit return, and the while
loops excecute. Is there a way to use return or /n or something as a
condition for escaping the loop.

On Feb 4, 10:26 pm, John B <jbngs...@yahoo.com> wrote:

mmoski wrote:

I'm still on the same program and I've cleared up many of the bugs
from before but I still have the same problem. I CAN'T GET OUT OF
THIS LOOP! I'm using System.in to read data from the console and I
can't find a break condition that works. There can be NO other user
input other than the data to be processed. Say a user enters "de ad
be ef". The program jumps into the loop which will run forever unless
it is broken. My problem is that I can't find a good way to tell the
computer "if(there is no more data to read from the console){break;}.
I've tried everything from if(sc.hasNext == false) to [input =
sc.next()] if(input == null) to breaking at the end of the loop and
trying to find conditions for continue; statements. HELP ME! I feel
like my head is about to burst.
I'm not the only one having this problem and everything I could dig up
on a solution involves the user inputting some keyword that forces a
break,
but I can't have any user input past the data entry.

How does the user know they are finished?
How do they tell the program this?
Somewhere there has to be a time based or user input signal that input
has finished.

<...>

JB

On a Windows machine you end console input with a CTRL-Z<ENTER>.

Unfortunately if you use Scanner to parse your input you can't detect
<ENTER> alone being pressed, with the default delimiter. So while you
see a linefeed on the console, hasNext() and next() report no input. If
you want to detect and empty line, just pressing <ENTER>, use a
BufferedReader. With the BR you can read in complete lines of text,
read a string with BufferedReader.readLine(), parse it with Scanner if
you wish, and test for .equals("") to detect an empty line.

import java.util.*;

public class test {
     public static void main(String[] args) {
         Scanner s = new Scanner(System.in);
         while (s.hasNext()) {
             s.next();
             System.out.println("next");
         }
     }
}

--

Knute Johnson
email s/nospam/knute/