Inspired by http://minborgsjavapot.blogspot.it/2016/03/put-your-java-8-method-references-to.html

Predicates.java

/*
This is an useful utility class to convert Method References to Functional References
Example:

// Processing Java Stream: Couting empty strings using Method references
Stream.of("A", "", "B").filter(String::isEmpty).count() --> result: 1

// But it is impossible to count non-empty string using the same method
There is no !String::isEmpty or String::isNotEmpty

// However using Java type references mechanism we can in-directly translate Method references to Functional references
// but, String::isEmpty can be translated to 1.Predicate<String> or 2.Function<String, Boolean>
// so we need to explicitly specify which Functional references it should be translated to.
// Using this below class, we can count non-empty string as:
Stream.of("A", "", "B").filter(Predicates.negate(String::isEmpty)).count() --> result: 2
*/

public final Predicates {
    private Predicates {}
  
    // convert Method reference to Functional reference
    public static <T> Predicate<T> of(final Predicate<T> predicate) {
        Objects.requireNonNull(predicate, "Predicate must be specified");
        return predicate;
    }
  
    public static <T> Predicate<T> negate(final Predicate<T> predicate) {
        Objects.requireNonNull(predicate, "Predicate must be specified");
        return predicate.negate();
    }
}