Locating data via pattern matching

[Harold Ndou]

import java.util.regex.*;
class Regex {
public static void main(String [] args){
Pattern p = Pattern.compile(args[0]) ;
Matcher m = p.matcher(args[1]);
System.out.println("Pattern is " + m.pattern());
while(m.find()) {
System.out.println(m.start() + m.group());
}
}
}

Here is the test run:
% java Regex "\d\w" "ab4 56_7ab"

The output is:

Pattern is \d\w
4 56
7 7a

Hi everyone

I have a problem with above code from k&b scjp 6 studyguide chapter 6 pg 499, i compile and run this code and i was expecting the above output, but i got an exception.

I would like to know where to put test run :

% java Regex "\d\w" "ab4 56_7ab" to get the above output .

I understand that d is looking for digit and w is looking for word character, am not clear about the output. Please can you explain to me, i will appriciate your assistance.

[Jeanne Boyarsky]

What exception did you get when running?

[Harold Ndou]

I got this:

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 0 at Regex.main<Regex.java:4>

[Jeanne Boyarsky]

Hmm. That means Java sin't recognizing your command line arguments. Are you running this at the command line or through an IDE?

[Harold Ndou]

I was running it on the textpad, how to do it on the command line

[Jeanne Boyarsky]

1) Open a command line
2) cd to the directory containing the program
3) type: java Regex "\d\w" "ab4 56_7ab"

Alternatively, the last line of this page says how to use Textpad to pass command line arguments.