Validation Example with BiFunction

BiFunctionValidationExample.java

import java.util.function.BiFunction;
import java.util.function.Function;

import static Pet.*;

public class BiFunctionValidationExample {

    public static void main(String[] args) {
        // BiFunction example
        BiFunctionValidation<Pet, String> v = new BiFunctionValidation<>(IS_EMPTY_RETURN_PET);
        System.out.println(v.validate(null, CAT));     // prints CAT
        System.out.println(v.validate(null, DOG));     // prints DOG
        System.out.println(v.validate("VALUE", DOG));  // prints null

        // Function example
        System.out.println(GET_PET.apply("dog"));
    }

}
enum Pet {
    CAT,
    DOG;

    /*
     *  Return Pet if String value is null
     */
    public static BiFunction<Pet, String, Pet> IS_EMPTY_RETURN_PET = (x, y) -> {
        if (y == null)
            return x;
        return null;
    };

    /*
     *  Return Pet matching string
     */
    public static Function<String, Pet> GET_PET = (x) -> valueOf(x.toUpperCase());

}
/*
 *  BiFunctionValidation<RETURN_OBJECT, VALUE_OBJECT>
 */
class BiFunctionValidation<R, V> {
    
    private BiFunction<R, V, R> biFunction;

    public BiFunctionValidation(BiFunction<R, V, R> biFunction) {
        this.biFunction = biFunction;
    }

    public R validate(V value, R r) {
        return biFunction.apply(r, value);
    }
}