196. Logging in predicates

We already know that the Predicate functional interface relies on its test() method to perform the given check, and it returns a Boolean value. Let’s suppose that we want to alter the test() method to log the failure cases (the cases that lead to the return of a false value).

A quick approach is to write a helper method that sneaks the logging part, as follows:

public final class Predicates {
  private static final Logger logger 
    = LoggerFactory.getLogger(LogPredicate.class);
  private Predicates() {
    throw new AssertionError("Cannot be instantiated");
  }
  public static <T> Predicate<T> testAndLog(
      Predicate<? super T> predicate, String val) {
    return t -> {
      boolean result = predicate.test(t);
      if (!result) {
        logger.warn(predicate + " don't match '" + val + "'");
      }
      return result;
    };
  }
}

Another approach consists of...