Regex pattern to match positive and negative number values in a String
java, negative-number, pattern-matching, regex
Solution
You absolutely can use a regular expression to capture negative numbers, but it depends on what you're trying to weed out.
"(?<=\\[)[^\\]]+|[-\\w]+"
The simplest way is to simply add '-' to the group of recognized word characters. However, this will also result in weird formations like '9-9' being legal. Considering you already match tokens like '9_9', I'm not sure that's a problem for you. I'd probably just add another alternation to the end of this regex:
"(?<=\\[)[^\\]]+|\\w+|-?\\d+"
Which allows an optional '-' character followed by at least one digit. Or, a negative number. This is fairly robust - you're literally just defining an additional type of match (a very specific one), but every time you find a new case, you really shouldn't just keep adding '|...' to the end of your regex. It's about the least efficient way to do what you're doing. It seems, in your situation, that this isn't really a problem, but you should think about this as your use case expands.
Problem
I have pattern/matcher lines that transform input Strings like this: ``` 1 3 Hi [2 1 4] ``` into an Array like this: ``` [0] => "1" [1] => "3" [2] => "Hi" [3] => "2 1 4" ``` That's the code: ``` String input = sc.nextLine(); Pattern p = Pattern.compile("(?<=\\[)[^\\]]+|\\w+"); Matcher m = p.matcher(input); List<String> cIn = new ArrayList<String>(); while(m.find()) cIn.add(m.group()); ``` Now I realised that sometimes I could get some negative values, inputs like `4 2 -1 2`. Since the input is a String, i can't really use any regular expression to get that negative value. Below in the code, I use ``` Integer.parseInt(cIn.get(0)); ``` to transform that string value into the Integer, that is actually what I need. Could you figure a way that allows me to keep together the `-` char and the number char? Then I would just check if there's the `-` char to transform the number and multiply it by `-1`. (If there's a better way I'd be glad to hear). As usual, excuse me for my English.