Regex for arithmetic expressions

Question

Hi all,
I am new to Java. I was wondering if anyone can help me understand how regular expressions work. My problem is how to come up with a regular expression that would match a simple arithmetic expression like:
a + b + c + d
And I want to capture things by groups. I largely suspect that I should use something like:
(\\w+)(\\s\\+\\s(\\w+))*
(I use the \\s here because \\b doesn't seem to work)
would work by capturing the first word like sequence with (\\w+), and the succeeding repeats of the plus sign and another word being captured by (\\s\\+\\s(\\w+))*. Didn't work though. Can anyone tell me what's wrong and how to think of a better way of handling these sort of expressions?
The code I tried goes like:
String patt = "(\\w+)(\\s\\+\\s(\\w+))*";
String feed = "a + b + c + d";
Pattern p = Pattern.compile(patt);
Matcher m = p.matcher(feed);
/* here I want to see if the groupings work somehow*/
if(m.find()){
for(int i=0; i<=m.groupCount(); i++)
System.out.println(m.group(i));
Thanks

Answer 1

Sorry about that. Here's the correctly formatted post:
So, with a simple arithmetic expression like:
a + b + c + dI want to capture things by groups and I thought of using something like:
(\\w+)(\\s\\+\\s(\\w+))*(I use the \\s here because \\b doesn't seem to work)
with the idea of capturing the first word like sequence with (\\w+), and the succeeding repeats of the plus sign and another word being captured by (\\s\\+\\s(\\w+))*. As this didn't work, can anyone tell me what's wrong and how to think of a better way of handling these sort of expressions?
The code I tried goes like:
String patt = "(\\w+)(\\s\\+\\s(\\w+))*";
String feed = "a + b + c + d";
Pattern p = Pattern.compile(patt);
Matcher m = p.matcher(feed);then I want to see if the groupings work somehow
if(m.find()){
for(int i=0; i<=m.groupCount(); i++)
System.out.println(m.group(i));
}and yes, I am wondering if arithmetic parsing would be possible with regex. I have implemented something similar before using combinations of simple tokenization and character checks, but I want to make cleaner looking code. Would using regular expressions be a bad choice? What if I feed something like:
(a + b) + (c + d)