CODEWITHSUNDEEP
java
W W
W W

Reputation: 799

String.matches() with \n

Why the String::matches method returns false when the string contains \n?

public class AppMain2 {

    public static void main(String[] args) {

        String data1 = "\n  London";    
        System.out.println(data1.matches(".*London.*")); // false
    }    
}

Upvotes: 4

Views: 1805

Answers (4)

Indent
Indent

Reputation: 4967

If you want matches to return true, you need to use (?s) or Pattern.DOTALL.

This way . matches any character including \n

System.out.println(data1.matches("(?s).*London.*"));

or:

Pattern pattern = Pattern.compile(".*London.*", Pattern.DOTALL);
System.out.println(data1.matches(pattern));

Upvotes: 5

Harsh Maheswari
Harsh Maheswari

Reputation: 517

"\n" considered as newline so String.matches searching for the pattern to in new line.so returning false try something like this.

Pattern.compile(".London.", Pattern.MULTILINE);

Upvotes: -1

lc.
lc.

Reputation: 116538

By default Java's . does not match newlines. To have . include newlines, set the Pattern.DOTALL flag with (?s):

System.out.println(data1.matches("(?s).*London.*"));

Note for those coming from other regex flavors, the Java documentation use of the term "match" is different from other languages. What is meant is Java's string::matches() returns true only if the entire string is matched, i.e. it behaves as if a ^ and $ were added to the head and tail of the passed regex, NOT simply that it contains a match.

Upvotes: 2

Venom
Venom

Reputation: 1060

It doesn't match because "." in regex may not match line terminators as in the documentation here :

https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html#sum

Upvotes: 2

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