Question

Pattern p2 = Pattern.compile(".*");
Matcher m2 = p2.matcher("true");
System.out.println(m2.matches() + " [" + m2.group() + "]");

When I use the code above it is all right. But I don’t understand what is going on when I use this regexpr [.]*. It prints false.

How to make a dot as a specific symbol? Or how to make a class of symbols with any characters without \n and \r?

Answer 1

But I don’t understand what is going on when I use this regexpr [.]*. It says me false.

Because inside a character class, the dot loses its special meaning and will match a plain old dot (the . character).

Outside of a character class the dot is a metacharacter that matches any character, excluding newlines (unless you use the Pattern.DOTALL modifier, of course).

Or how to make a class of symbols with any characters without \n and \r.

Use a negated character class:

 Pattern p2 = Pattern.compile("[^\\r\n]*");

[^\r\n] means “match anything that’s not a \r or a \n.