How to split a comma separated String while ignoring escaped commas?

Question

I need to write a extended version of the StringUtils.commaDelimitedListToStringArray function which gets an additional parameter: the escape char.

so calling my:

commaDelimitedListToStringArray("test,test\\,test\\,test,test", "\\") 

should return:

["test", "test,test,test", "test"] 

My current attempt is to use String.split() to split the String using regular expressions:

String[] array = str.split("[^\\\\],"); 

But the returned array is:

["tes", "test\,test\,tes", "test"] 

Any ideas?

Answer 1

The regular expression

[^\\], 

means "match a character which is not a backslash followed by a comma" - this is why patterns such as t, are matching, because t is a character which is not a backslash.

I think you need to use some sort of negative lookbehind, to capture a , which is not preceded by a \ without capturing the preceding character, something like

(?<!\\), 

(BTW, note that I have purposefully not doubly-escaped the backslashes to make this more readable)