Question

I have the following (Java) code:

public class TestBlah {
    private static final String PATTERN = ".*\\$\\{[.a-zA-Z0-9]+\\}.*";

    public static void main(String[] s) throws IOException {
        String st = "foo ${bar}\n";

        System.out.println(st.matches(PATTERN));
        System.out.println(Pattern.compile(PATTERN).matcher(st).find());
        System.exit(0);
    }
}

Running this code, the former System.out.println outputs false, while the latter outputs true

Am I not understanding something here?

Answer 1

This is because the . will not match the new line character. Thus, your String that contains a new line, will not match a string that ends with .*. So, when you call matches(), it returns false, because the new line doesn’t match.

The second one returns true because it finds a match inside the input string. It doesn’t necessarily match the whole string.

From the Pattern javadocs:

. Any character (may or may not match line terminators)