What's the difference between String.matches and Matcher.matches?

Question

What\'s the difference between String.matches and Matcher.matches? Is there any difference in terms of performance or other things?

Answer 1

String.matches internally delegates to Matcher.matches.

public boolean matches(String regex) {
    return Pattern.matches(regex, this);
}

public static boolean matches(String regex, CharSequence input) {
    Pattern p = Pattern.compile(regex);
    Matcher m = p.matcher(input);
    return m.matches();
}

If you are reusing the Pattern object then there will be some performance benefit. Also when using Pattern/Matcher you can group your regular expressions and get the matching parts.

The bottomline is if you have a regex that you will use only once and you don't need to parse your string to get matching parts then use either. But if you are going to use the same regex against multiple strings or you need parts of the String based on regex create a Pattern and get Matcher using it.