How to split this string using Java Regular Expressions

Question

I want to split the string

String fields = "name[Employee Name], employeeno[Employee No], dob[Date of Birth], joindate[Date of Joining]";

to

name
employeeno
dob
joindate

I wrote the following java code for this but it is printing only name other matches are not printing.

String fields = "name[Employee Name], employeeno[Employee No], dob[Date of Birth], joindate[Date of Joining]";

Pattern pattern = Pattern.compile("\\[.+\\]+?,?\\s*" );

String[] split = pattern.split(fields);
for (String string : split) {
    System.out.println(string);
}

What am I doing wrong here?

Thank you

Answer 1

This part:

\\[.+\\]

matches the first [, the .+ then gobbles up the entire string (if no line breaks are in the string) and then the \\] will match the last ].

You need to make the .+ reluctant by placing a ? after it:

Pattern pattern = Pattern.compile("\\[.+?\\]+?,?\\s*");

And shouldn't \\]+? just be \\] ?

Answer 2

The error is that you are matching greedily. You can change it to a non-greedy match:

Pattern.compile("\\[.+?\\],?\\s*")
                      ^

Answer 3

There's an online regular expression tester at http://gskinner.com/RegExr/?2sa45 that will help you a lot when you try to understand regular expressions and how they are applied to a given input.

Answer 4

WOuld it be better to use Negated Character Classes to match the square brackets? \[(\w+\s)+\w+[^\]]\]

You could also see a good example how does using a negated character class work internally (without backtracking)?