Java Regex: Capture Multiple Matches on the same Line

Question

I am trying to create a regex expression that would match one or multiple variable value assignments on the same line. I am using the following expression:

([a-z][a-zA-Z0-9-]*)=(('(\'|[^\'])*')|("(\"|[^"])*"))

For example, if I have the following string as input:

a="xyz" b="hello world"

And using the following code:

Matcher matcher = rules.get(regex).matcher(input);
int start = 0;

while (matcher.find(start)) {
    System.err.println(matcher.group(0));

    start = matcher.end();
}

It should give me two seperate results:

1. a="xyz"
2. b="hello world"

But it only returns one, the entire input string.

a="xyz" b="hello world"

It seems to be taking xyz" b="hello world as the inner part. How can I resolve this?

Your alternatives are off, see ([a-z][a-zA-Z0-9-]*)=(('([^']*)')|("([^"]*)")), demo — Wiktor Stribiżew
– Wiktor Stribiżew, Commented Mar 4, 2020 at 21:43
@WiktorStribiżew It was a mistake in typing the pattern, check again because mine is a bit different. — Omari Celestine
– Omari Celestine, Commented Mar 4, 2020 at 21:53

Wiktor Stribiżew · Accepted Answer · 2020-03-04 21:56:08Z

You may use

(?s)([a-z][a-zA-Z0-9-]*)=(?:'([^\\']*(?:\\.[^\\']*)*)'|"([^"\\]*(?:\\.[^"\\]*)*)")

See the regex demo

In Java,

String regex = "(?s)([a-z][a-zA-Z0-9-]*)=(?:'([^\\\\']*(?:\\\\.[^\\\\']*)*)'|\"([^\"\\\\]*(?:\\\\.[^\"\\\\]*)*)\")";

Details

(?s) - inline Pattern.DOTALL embedded flag option that matches . match line break chars, too
([a-z][a-zA-Z0-9-]*) - Group 1
= - an equals sign
(?:'([^\\']*(?:\\.[^\\']*)*)'|"([^"\\]*(?:\\.[^"\\]*)*)") - a non-capturing group matching one of the two alternatives:
- '([^\\']*(?:\\.[^\\']*)*)' - ', then any amount of chars other than \ and ' followed with 0+ repetitions of any escape sequence followed with 0+ chars other than \ and '
- | - or
- "([^"\\]*(?:\\.[^"\\]*)*)" - ", then any amount of chars other than \ and " followed with 0+ repetitions of any escape sequence followed with 0+ chars other than \ and " .

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