predicate

In Java 8, you can use a method reference to filter a stream, for example: Stream<String> s = ...; long emptyStrings = s.filter(String::isEmpty).count(); Is there a way to create a method reference that is the negation of an existing one, i.e. something like: long nonEmptyStrings = s.filter(not(String::isEmpty)).count(); I could create the not method like below but I was wondering if the JDK offered something similar. static <T> Predicate<T> not(Predicate<T> p) { return o -> !p.test(o); } Anton Balaniuc Predicate.not( … ) java-11 offers a new method Predicate#not So you can negate the method

This question already has an answer here: Sequence find function in Python 4 answers I want an idiomatic way to find the first element in a list that matches a predicate. The current code is quite ugly: [x for x in seq if predicate(x)][0] I've thought about changing it to: from itertools import dropwhile dropwhile(lambda x: not predicate(x), seq).next() But there must be something more elegant... And it would be nice if it returns a None value rather than raise an exception if no match is found. I know I could just define a function like: def get_first(predicate, seq): for i in seq: if

This is a simplified version of the original problem. I have a class called Person: public class Person { public string Name { get; set; } public int Age { get; set; } public int Weight { get; set; } public DateTime FavouriteDay { get; set; } } ...and lets say an instance: var bob = new Person { Name = "Bob", Age = 30, Weight = 213, FavouriteDay = '1/1/2000' } I would like to write the following as a string in my favourite text editor.... (Person.Age > 3 AND Person.Weight > 50) OR Person.Age < 3 I would like to take this string and my object instance and evaluate a TRUE or FALSE - i.e.