Java Regex：匹配行首

Question

I am reading through a number of text files that are a dump of e-mail messages. I am trying to check if the line I am reading starts with "Cc:". For example I would want to match the following example line "Cc:\\temail1@example.com; email2@exmaple.com".

The code that I am using looks like this:

Pattern pattern = Pattern.compile("^Cc\\:");
line = reader.readLine();

if (pattern.matcher(line).matches()) {
   System.out.println(line);
}

Any idea why this is not matching?

Answer 1

There's nothing wrong with your regex per se (although you have unnecessarily escaped the colon, but bit will still work), but the reason it's not working is that in java (unlike most other popular languages) matches() must match the whole string. Change your regex to "Cc:.*" . Note how in java you don't need the ^ or $ because they are implied due to having to match the whole string.

However, for a simpler case-insensitive check using regex:

if (line.matches("(?i)cc:.*")) // note the .*

Or without regex:

if (line.toLowerCase().startsWith("cc:"))