How to use \R in java 8 regex [duplicate] - regex

Question

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Difference between matches() and find() in Java Regex
(5 answers)
Closed 5 years ago.
I am trying to use the new \R regex matcher from java 8.
However, for the following code :
public static void main(String[] args)
{
String s = "This is \r\n a String with \n Different Newlines \r and other things.";
System.out.println(s);
System.out.println(Pattern.matches("\\R", s));
if (Pattern.matches("\\R", s)) // <-- is always false
{
System.out.println("Matched");
}
System.out.println(s.replaceAll("\\R", "<br/>")); //This is a String with <br/> Different Newlines <br/> and other things.
}
The Pattern.matches always returns false, where as the replaceAll method does seem to find a match and does what I want it to. How do I make the Pattern.matches work ?
I have also tried the long about way and still can't get it to work :
Pattern p = Pattern.compile("\\R");
Matcher m = p.matcher(s);
boolean b = m.matches();
System.out.println(b);

Answer 1

Well matches (both in String and Matchers classes) attempts to match the complete input string.
You need to use matcher.find instead:
Pattern p = Pattern.compile("\\R");
Matcher m = p.matcher(s);
boolean b = m.find();
System.out.println(b);
From Java docs:
\R Matches any Unicode line-break sequence, that is equivalent to \u000D\u000A|[\u000A\u000B\u000C\u000D\u0085\u2028\u2029]
PS; If you want to know if input contains a line-break then this one liner will work for you:
boolean b = s.matches("(?s).*?\\R.*");
Note use of .* on either side of \R to make sure we are matching complete input. Also you need (?s) to enable DOTALL mode to be able to match multiline string with .*