Using the new java 1.5 Scanner class is tricky if you want it to stop reading input when it reaches a blank line. To do this, use two nested java.util.Scanner instances, one to read lines, the other to parse each line:

import java.util.*;
public class Test{
	public static void main(String [] args){
		Scanner s = new Scanner(System.in);

		while(s.hasNextLine()){
			Scanner ss = new Scanner(s.nextLine());

			if(!ss.hasNext())
				break;
				// line empty, quit

			while(ss.hasNext()){
				// handle input types
				ss.next();
			}

			ss.close();
		}

		System.err.println("Done program");
		s.close();
	}
}

That’s all there is to a complicated use of Scanner for line-by-line text tokenization!

5 Responses to “Using Scanner to stop reading input on a blank line”

1. atif says:

   3/3/2011 at 3:43 pm

   Thanks a ton for the code, saved me a lot of trouble

   Reply
2. Daniel says:

   7/25/2010 at 9:18 pm

   Thanks

   Reply
3. tomk says:

   2/12/2010 at 5:56 pm

   thx a lot, discovered this a bit too late, but still great to know why my scanner input didnt work for blank lines.

   Reply
4. greg says:

   10/2/2007 at 1:19 am

   another computer science project saved thanks to this code. cheers!

   Reply
5. chris stoll says:

   2/12/2007 at 3:54 am

   Oh god, this saved me on a computer science project. I had to edit it quite a bit to fit my application. Thanks for the insight!

   Reply