CODEWITHSUNDEEP
javaregexstringsplit
shinzou
shinzou

Reputation: 6202

Splitting a string of coordinates and signs

I want to split a line of coordinates and signs like: (4, 9) ?, (741, 5) +, (555, 82) -,

To be split to the following parts: 4, 9, ?, 741, 5, +, 555, 82, -

So I came up with this expression: ",(?=([0-9]+))|(?<=([0-9]+)),| +|\\(|\\)?" but it matches digits instead of numbers and a lot of empty strings... How can I fix it?

The expression is supposed to match a number if there's a , behind or infront of it, and the other +-? signs.

This is using String.split().

Upvotes: 1

Views: 98

Answers (2)

user94559
user94559

Reputation: 60143

Instead of splitting, how about just searching for what you're looking for?

import java.util.regex.Matcher;
import java.util.regex.Pattern;

public class Test {
    public static void main(String... args) {
        String input = "(4, 9) ?, (741, 5) +, (555, 82) -,";
        Matcher matcher = Pattern.compile("[\\d?+\\-]+").matcher(input);
        while (matcher.find()) {
            System.out.println(matcher.group());
        }
    }
}

// Output:
// 4
// 9
// ?
// 741
// 5
// +
// 555
// 82
// -

Depending on your input, this regular expression may be even better:

\\d+|[?+\\-]

For the given input, the result is the same, but this version would mean sequences like "45-8" result in three matches (45, -, and 8) instead of just one (45-8).

Upvotes: 2

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626950

Here is a split solution:

String s = "(4, 9) ?, (741, 5) +, (555, 82) -,";
String pat = "[\\D&&[^+?-]]+";
String[] res = s.replaceFirst("^"+pat, "").split(pat);
System.out.println(Arrays.toString(res));

See the regex demo

The [\D&&[^+?-]]+ pattern matches one or more non-digit symbols except +, ?, -. The replaceFirst with a ^ anchor prepended to the pattern removes the matches from the start of the string to get rid of an empty array element in the result. The &&[^...] here is a character class subtraction syntax, we match all what is before except what is after ^. Note that \D (any non-digit) is equal to [^\d] (any character other than a digit) thus, you can actually write the same pattern as [^\d+?-].

Since you asked:

Can we apply de morgan on this and use the expression "a number or +-?"?

It depends on what you mean by a number, but it is possible you want to match a chunk of digits, OR a +, - or ?. In this case, you really need an alternation: \d+|[-?+].

String rx = "\\d+|[-?+]";
List<String> lst = new ArrayList<>();
Pattern p = Pattern.compile(rx);
Matcher m = p.matcher("(4, 9) ?, (741, 5) +, (555, 82) -,");
while (m.find()) {
    lst.add(m.group(0));
}
System.out.println(lst);

See Java demo

Upvotes: 1

Related Questions