Using RegEx split the string

Question

I have a string like '[1]-[2]-[3],[4]-[5],[6,7,8],[9]' or '[Computers]-[Apple]-[Laptop],[Cables]-[Cables,Connectors],[Adapters]', I'd like the Pattern to get the list result, but don't know how to figure out the pattern. Basically the comma is the split, but [6,7,8] itself contains the comma as well.

the string: [1]-[2]-[3],[4]-[5],[6,7,8],[9]
the result:
[1]-[2]-[3]
[4]-[5]
[6,7,8]
[9]

or

the string: [Computers]-[Apple]-[Laptop],[Cables]-[Cables,Connectors],[Adapters]
the result:
[Computers]-[Apple]-[Laptop]
[Cables]-[Cables,Connectors]
[Adapters]

Oh, I see. This isn't really regex, you can use a simple split. — Christian Stewart
– Christian Stewart, Commented Mar 23, 2013 at 4:44
the splitter should work, but i want to use the Pattern, like RegEx.match — user1629480
– user1629480, Commented Mar 23, 2013 at 4:53
The question is unclear. "[1]" is a regex. Or do you mean that [1] stands in for the first list item? Or is 1 the list items, and the brackets and the dashes are literals? — Joshua Clayton
– Joshua Clayton, Commented Mar 23, 2013 at 4:55
Hi Joshua, the last part is the result i should get from the Pattern. and all the brackets and dashes are literals — user1629480
– user1629480, Commented Mar 23, 2013 at 5:01

j__m · Accepted Answer · 2013-03-23 05:33:49Z

3

,(?=\[)

This pattern splits on any comma that is followed by a bracket, but keeps the bracket within the result text.

The (?=*stuff*) is known as a "lookahead assertion". It acts as a condition for the match but is not itself part of the match.

In C# code:

String inputstring = "[Computers]-[Apple]-[Laptop],[Cables]-[Cables,Connectors],[Adapters]";
foreach(String s in Regex.Split(inputstring, @",(?=\[)"))
    System.Console.Out.WriteLine(s);

In Java code:

String inputstring = "[Computers]-[Apple]-[Laptop],[Cables]-[Cables,Connectors],[Adapters]";
Pattern p = Pattern.compile(",(?=\\[)"));
for(String s : p.split(inputstring))
    System.out.println(s);

Either produces:

[Computers]-[Apple]-[Laptop]
[Cables]-[Cables,Connectors]
[Adapters]

edited Mar 23, 2013 at 5:33

answered Mar 23, 2013 at 4:47

j__m

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9 Comments

user1629480 Over a year ago

i have a pattern, but it will split the [6,7,8] into three parts, it is ""[^""\r\n]*""|'[^'\r\n]*'|[^,\r\n]*

j__m Over a year ago

My pattern specifically preserves [6,7,8]

user1629480 Over a year ago

could you be able to elaborate your pattern please. i tried your pattern, but it does not work

John Dvorak Over a year ago

Perhaps it should be -(?=\[)? That is, a hyphen that is followed by a bracket?

user1629480 Over a year ago

Sorry, i should mention i have to use the Pattern, not Split. there should be a Pattern, but cannot figure it out yet. anyway thanks for your code example :)

|

FThompson · Accepted Answer · 2013-03-23 05:51:48Z

0

Although I believe the best approach here is to use split (as presented by @j__m's answer), here's an approach that uses matching rather than splitting.

Regex:

(\[.*?\](?!-))

Example usage:

String input = "[Computers]-[Apple]-[Laptop],[Cables]-[Cables,Connectors],[Adapters]";
Pattern p = Pattern.compile("(\\[.*?\\](?!-))");
Matcher m = p.matcher(input);
while (m.find()) {
    System.out.println(m.group(1));
}

Resulting output:

[Computers]-[Apple]-[Laptop]
[Cables]-[Cables,Connectors]
[Adapters]

answered Mar 23, 2013 at 5:51

FThompson

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1 Comment

user1629480 Over a year ago

thanks for that. it is exactly what i want. you are champion : )

composerMike · Accepted Answer · 2013-03-23 04:53:13Z

0

An answer that doesn't use regular expressions (if that's worth something in ease of understanding what's going on) is:

substitute "]@[" for "],["
split on "@"

answered Mar 23, 2013 at 4:53

composerMike

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1 Comment

FThompson Over a year ago

And if the string has any @ symbols to begin with, you're out of luck. The other answer offers a far better solution that doesn't encounter this issue.

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