problems with regex

[susana miranda]

Hi everybody! this is my first post
and... I have this class

import java.util.regex.*;
import java.io.*;

public class Regex{
	public static void main(String args[]){
	Console c = System.console();
	String myPattern = c.readLine("Pattern: ");
	Pattern p = Pattern.compile(myPattern);
	String mySource = c.readLine("Source: ");
	Matcher m = p.matcher(mySource);
	while (m.find()){
		System.out.print("start: "+m.start());
		System.out.println(" ---group: "+m.group());
	}	
    }

}

I understand the result of my first execution:

% /SCJP/exercises$ java Regex
Pattern: \d+
Source: 123a456b78ccc0
start: 0 ---group: 123
start: 4 ---group: 456
start: 8 ---group: 78
start: 13 ---group: 0

but not the second

% /SCJP/exercises$ java Regex
Pattern: \d*
Source: 123a456b78ccc90
start: 0 ---group: 123
start: 3 ---group:
start: 4 ---group: 456
start: 7 ---group:
start: 8 ---group: 78
start: 10 ---group:
start: 11 ---group:
start: 12 ---group:
start: 13 ---group: 90
start: 15 ---group:

Why with \d* it returns an empty group if with \d i mean only numbers. I am a little confused :s

[Harpreet Singh janda]

Please use code tag to post the code like

        import java.util.regex.*;
        import java.io.*;
        public class Regex{
	public static void main(String args[]){
		Console c = System.console();
		String myPattern = c.readLine("Pattern: ");
		Pattern p = Pattern.compile(myPattern);
		String mySource = c.readLine("Source: ");
		Matcher m = p.matcher(mySource);
		while (m.find()){
			System.out.print("start: "+m.start());
			System.out.println(" ---group: "+m.group());
		}
	}

} 

[Harpreet Singh janda]

* means 0 or more

So it will consider each element of line as eligible.

[susana miranda]

Ok Harpreet. Thanks a lot. I had misunderstood * Only one more question:
Why on the second execution returns position start: 15? If my source ends with 90. Is it because null counts or so?

% /SCJP/exercises$ java Regex
Pattern: \d*
Source: 123a456b78ccc90
start: 0 ---group: 123
start: 3 ---group:
start: 4 ---group: 456
start: 7 ---group:
start: 8 ---group: 78
start: 10 ---group:
start: 11 ---group:
start: 12 ---group:
start: 13 ---group: 90
start: 15 ---group:

[Harpreet Singh janda]

Yes, as you know * means 0 or more and after 90 there is nothing so it will be counted.

[susana miranda]

Ok, thanks a lot.