import java.util.regex.Pattern;
import java.util.regex.PatternSyntaxException;

/**
 * File name filter that only accepts files matching a regular expression. This class is thread-safe
 * and immutable.
 *
 * @author Apple Chow
 * @since 1.0
 */
@J2ktIncompatible
@GwtIncompatible
@ElementTypesAreNonnullByDefault
public final class PatternFilenameFilter implements FilenameFilter {

  private final Pattern pattern;

  /**

knowledge.  `Just think of what work it would make with the day
and night!  You see the earth takes twenty-four hours to turn
round on its axis--'

  `Talking of axes,' said the Duchess, `chop off her head!'

  Alice glanced rather anxiously at the cook, to see if she meant
to take the hint; but the cook was busily stirring the soup, and
seemed not to be listening, so she went on again:  `Twenty-four

      return new Chopper() {
        @Override
        Optional<String> chop(String str) {
          return i.chop(str).or(you.chop(str));
        }
      };
    }

    abstract Optional<String> chop(String str);

    static Chopper suffix(String suffix) {
      return new Chopper() {
        @Override
        Optional<String> chop(String str) {
          if (str.endsWith(suffix)) {

      return new Chopper() {
        @Override
        Optional<String> chop(String str) {
          return i.chop(str).or(you.chop(str));
        }
      };
    }

    abstract Optional<String> chop(String str);

    static Chopper suffix(String suffix) {
      return new Chopper() {
        @Override
        Optional<String> chop(String str) {
          if (str.endsWith(suffix)) {

knowledge.  `Just think of what work it would make with the day
and night!  You see the earth takes twenty-four hours to turn
round on its axis--'

  `Talking of axes,' said the Duchess, `chop off her head!'

  Alice glanced rather anxiously at the cook, to see if she meant
to take the hint; but the cook was busily stirring the soup, and
seemed not to be listening, so she went on again:  `Twenty-four