java - Regular expression does not match newline obtained from Formatter object

Question

I cannot match a String containing newlines when the newline is obtained by using %n in Formatter object or String.format(). Please have a look at the following program:

public class RegExTest {

  public static void main(String[] args) {
    String input1 = String.format("Hallo
next line");
    String input2 = String.format("Hallo%nnext line");
    String pattern = ".*[

].*";
    System.out.println(input1+": "+input1.matches(pattern));
    System.out.println(input2+": "+input2.matches(pattern));
  }

}

and its output:

Hallo
next line: true
Hallo
next line: false

What is going on here? Why doesn't the second string match?

Java version is 1.6.0_21.

Answer 1

You can set the Pattern.DOTALL flag to make . match newlines, as default it doesn't. It is done with the (?s) notation. So, this regex does what you want:

    String pattern = "(?s).*[

].*";