How to split comma-separated string but exclude some words containing comma in Java

Question

Assume that we have below string:

"test01,test02,test03,exceptional,case,test04"

What I want is to split the string into string array, like below:

["test01","test02","test03","exceptional,case","test04"]

How can I do that in Java?

Answer 1

This negative lookaround regex should work for you:

(?<!exceptional),|,(?!case)

Working Demo

Java Code:

String[] arr = str.split("(?<!exceptional),|,(?!case)");

Explanation:

This regex matches a comma if any one of these 2 conditions meet :

1. comma is not preceded by word exceptional using negative lookbehind (?<!exceptional)
2. comma is not followed by word case using negative lookahead (?!case)

That effectively disallows splitting on comma when it is surrounded by exceptional and case on either side.

Answer 2

@anubhava's answer is great—use it. For completion, here's a general solution that is applicable to many solutions and uses a beautifully simple regex:

exceptional,case|(,)

The left side of the alternation | matches complete exceptional,case . We will ignore these matches. The right side matches and captures commas to Group 1, and we know they are the right ones because they were not matched by the expression on the left. We then replace these commas by something distinctive, and split on that string.

This program shows how to use the regex (see the results at the bottom of the online demo ):

 String subject = "somethingelse,case,test02,test03,exceptional,case,test04,exceptional,notcase";
Pattern regex = Pattern.compile("exceptional,case|(,)");
Matcher m = regex.matcher(subject);
StringBuffer b= new StringBuffer();
while (m.find()) {
if(m.group(1) != null) m.appendReplacement(b, "@@SplitHere@@");
else m.appendReplacement(b, m.group(0));
}
m.appendTail(b);
String replaced = b.toString();
String[] splits = replaced.split("@@SplitHere@@");
for (String split : splits) System.out.println(split);

Reference

• How to match (or replace) a pattern except in situations s1, s2, s3...
• Article about matching a pattern unless...

Answer 3

How can Java understand the exceptional,case is a single word and not to split ?

Still If there would have been some other recurring character like "" you could have split it.

For ex. if It was

"test01","test02","test03","exceptional,case","test04"

You could split it using ","

So in your case it is not possible, unless you use regular expression.

Answer 4

Here's a dead-simple answer, don't know why I didn't think of it yesterday:

(?<!exceptional(?=,case)),

Explanation

A comma (the last character of the regex) that is not preceded by exceptional followed by ,case

Answer 5

String s1 = "test01.test02.test03.{i}.case.test04.test03.{i}.test03.{i}.test03.{i}";
String[] arr1 =    s1.split("(?<!)\\.|\\.(?!\\{i})");

    Output:
    test01
    test02
    test03.{i}
    case
    test04
    test03.{i}
    test03.{i}
    test03.{i}

Answer 6

You probably want to use split()

Like this:

String[] array = "test01,test02,test03,exceptional,case,test04".split(",");