String split if the first character is minus then tread it as a negative sign

Question

- sign can be treated as operator or negative sign. If - is located in the start, it shall be treated as the negative sign and a subtraction whiting the string. This is only apply to - sign while the + will be always the add sign. How can I achieve this?

input:

-23-23+4=F1Qa;
+23-23+4=F1Qa;

output:

["-23","-","23","+","4","=","F","1","Q","a",";"]
["+", "23","-","23","+","4","=","F","1","Q","a",";"]

This is what I've tried so far

String regx = (?:# .*? #:?)|(?!^)(?=\\D)|(?<=\\D)(?=\\d-)
String[] splits = inputString.split(regx);

Answer 1

You can use the regex, ^-\d+|\d+|\D which means either negative integer in the beginning (i.e. ^-\d+) or digits (i.e. \d+) or a non-digit (\D).

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

public class Main {

    public static void main(String[] args) {
        String str = "-23-23+4=F1Qa;";
        Pattern pattern = Pattern.compile("^-\\d+|\\d+|\\D");
        Matcher matcher = pattern.matcher(str);
        while (matcher.find()) {
            System.out.println(matcher.group());
        }
    }
}

Output:

-23
-
23
+
4
=
F
1
Q
a
;

Another test:

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

public class Main {

    public static void main(String[] args) {
        String str = "+23-23+4=F1Qa;";
        Pattern pattern = Pattern.compile("^-\\d+|\\d+|\\D");
        Matcher matcher = pattern.matcher(str);
        while (matcher.find()) {
            System.out.println(matcher.group());
        }
    }
}

Output:

+
23
-
23
+
4
=
F
1
Q
a
;