Using Regular Expression in java

[gjain12]

Hi All,

I have a string in which I have to find all the commas except the one which is followed by "space". I have tried ",[^ ], but it finds the patterns that start with , and one character.
e.g If my string is abc,bef, ghi,jkl,,mno
the it returns ',b' ',j' and ',,' while I want only ',' so that it can search from the next element in the string. Means it should return ',' ',' ','.

Thanks
Gaurav

[r035198x]

Try the negative look behind pattern "(?<! ),";

[gjain12]

Actually I am very novice to regular expression.
If you can provide me some exampl sort of for the same, it will be really helpful.

[r035198x]

Now that I've read your post again I realize that you said followed by a space not preceded by a space.
You need the negative look ahead instead.

                String p = ",(?! )";
        String input = "abc,bef, ghi,jkl, ,mno";
        Pattern pattern = Pattern.compile(p);
        Matcher matcher = pattern.matcher(input);
        boolean found = false;
        while (matcher.find()) {
            System.out.format("I found the text \"%s\" starting at " + "index %d and ending at index %d.%n", matcher.group(), matcher.start(), matcher.end());
            found = true;
        }
        if (!found) {
            System.out.format("No match found.%n");
        }
 

[gjain12]

Thanks a lot..
It works perfectly...
But I couldn't iunderstand how this regex is working.
Means how should I read this expression.
If you can explain it also it will be a great leraning experience.

[r035198x]

See the entries for those things in the regex tutorial.