Regular expression doesn't match empty string in multiline mode (Java)

Question

I just observed this behavior;

Pattern p1 = Pattern.compile(\"^$\");
Matcher m1 = p1.matcher(\"\");
System.out.println(m1.matches()); /* true */

Pattern p2         


        

Answer 1

If MULTILINE mode is activated then ^ matches at the beginning of input and after any line terminator except at the end of input.

Since you are at the end of input, ^ can't match in multiline mode.

This is surprising, even disgusting, but nevertheless according to its documentation.