Classes for matching character sequences against patterns specified by regular expressions.

An instance of the {@link java.util.regex.Pattern} class represents a regular expression that is specified in string form in a syntax similar to that used by Perl.

Instances of the {@link java.util.regex.Matcher} class are used to match character sequences against a given pattern. Input is provided to matchers via the {@link java.lang.CharSequence} interface in order to support matching against characters from a wide variety of input sources.

Unless otherwise noted, passing a `null` argument to a method in any class or interface in this package will cause a {@link java.lang.NullPointerException NullPointerException} to be thrown.

## Related Documentation

An excellent tutorial and overview of regular expressions is Mastering Regular Expressions, Jeffrey E. F. Friedl, O'Reilly and Associates, 1997.

@since 1.4 @author Mike McCloskey @author Mark Reinhold