Stream.of("A", "", "B").filter(String::isEmpty).count()

Stream.of("A", "", "B").filter(s -> !s.isEmpty()).count()

Predicate<String>
Function<String, Boolean>

public static <T> Predicate<T> as(Predicate<T> predicate) {
 return predicate;
}

Stream.of("A", "", "B").filter(as(String::isEmpty).negate()).count();

.filter(as(String::isEmpty).negate().and("A"::equals))

import java.util.function.*;

public class FunctionCastUtil {
 public static <T, U> BiConsumer<T, U> asBiConsumer(BiConsumer<T, U> biConsumer) {
 return biConsumer;
 }
 public static <T, U, R> BiFunction<T, U, R> asBiFunction(BiFunction<T, U, R> biFunction) {
 return biFunction;
 }
 public static <T> BinaryOperator<T> asBinaryOperator(BinaryOperator<T> binaryOperator) {
 return binaryOperator;
 }
 public static <T, U> BiPredicate<T, U> asBiPredicate(BiPredicate<T, U> biPredicate) {
 return biPredicate;
 }
 public static BooleanSupplier asBooleanSupplier(BooleanSupplier booleanSupplier) {
 return booleanSupplier;
 }
 public static <T> Consumer<T> asConsumer(Consumer<T> consumer) {
 return consumer;
 }
 public static DoubleBinaryOperator asDoubleBinaryOperator(DoubleBinaryOperator doubleBinaryOperator) {
 return doubleBinaryOperator;
 }
 public static DoubleConsumer asDoubleConsumer(DoubleConsumer doubleConsumer) {
 return doubleConsumer;
 }
 public static <R> DoubleFunction<R> asDoubleFunction(DoubleFunction<R> doubleFunction) {
 return doubleFunction;
 }
 public static DoublePredicate asDoublePredicate(DoublePredicate doublePredicate) {
 return doublePredicate;
 }
 public static DoubleToIntFunction asDoubleToIntFunction(DoubleToIntFunction doubleToIntFunctiontem) {
 return doubleToIntFunctiontem;
 }
 public static DoubleToLongFunction asDoubleToLongFunction(DoubleToLongFunction doubleToLongFunction) {
 return doubleToLongFunction;
 }
 public static DoubleUnaryOperator asDoubleUnaryOperator(DoubleUnaryOperator doubleUnaryOperator) {
 return doubleUnaryOperator;
 }
 public static <T, R> Function<T, R> asFunction(Function<T, R> function) {
 return function;
 }
 public static IntBinaryOperator asIntBinaryOperator(IntBinaryOperator intBinaryOperator) {
 return intBinaryOperator;
 }
 public static IntConsumer asIntConsumer(IntConsumer intConsumer) {
 return intConsumer;
 }
 public static <R> IntFunction<R> asIntFunction(IntFunction<R> intFunction) {
 return intFunction;
 }
 public static IntPredicate asIntPredicate(IntPredicate intPredicate) {
 return intPredicate;
 }
 public static IntSupplier asIntSupplier(IntSupplier intSupplier) {
 return intSupplier;
 }
 public static IntToDoubleFunction asIntToDoubleFunction(IntToDoubleFunction intToDoubleFunction) {
 return intToDoubleFunction;
 }
 public static IntToLongFunction asIntToLongFunction(IntToLongFunction intToLongFunction) {
 return intToLongFunction;
 }
 public static IntUnaryOperator asIntUnaryOperator(IntUnaryOperator intUnaryOperator) {
 return intUnaryOperator;
 }
 public static LongBinaryOperator asLongBinaryOperator(LongBinaryOperator longBinaryOperator) {
 return longBinaryOperator;
 }
 public static LongConsumer asLongConsumer(LongConsumer longConsumer) {
 return longConsumer;
 }
 public static <R> LongFunction<R> asLongFunction(LongFunction<R> longFunction) {
 return longFunction;
 }
 public static LongPredicate asLongPredicate(LongPredicate longPredicate) {
 return longPredicate;
 }
 public static <T> LongSupplier asLongSupplier(LongSupplier longSupplier) {
 return longSupplier;
 }
 public static LongToDoubleFunction asLongToDoubleFunction(LongToDoubleFunction longToDoubleFunction) {
 return longToDoubleFunction;
 }
 public static LongToIntFunction asLongToIntFunction(LongToIntFunction longToIntFunction) {
 return longToIntFunction;
 }
 public static LongUnaryOperator asLongUnaryOperator(LongUnaryOperator longUnaryOperator) {
 return longUnaryOperator;
 }
 public static <T> ObjDoubleConsumer<T> asObjDoubleConsumer(ObjDoubleConsumer<T> objDoubleConsumer) {
 return objDoubleConsumer;
 }
 public static <T> ObjIntConsumer<T> asObjIntConsumer(ObjIntConsumer<T> objIntConsumer) {
 return objIntConsumer;
 }
 public static <T> ObjLongConsumer<T> asObjLongConsumer(ObjLongConsumer<T> objLongConsumer) {
 return objLongConsumer;
 }
 public static <T> Predicate<T> asPredicate(Predicate<T> predicate) {
 return predicate;
 }
 public static <T> Supplier<T> asSupplier(Supplier<T> supplier) {
 return supplier;
 }
 public static <T, U> ToDoubleBiFunction<T, U> asToDoubleBiFunction(ToDoubleBiFunction<T, U> toDoubleBiFunction) {
 return toDoubleBiFunction;
 }
 public static <T> ToDoubleFunction<T> asToDoubleFunction(ToDoubleFunction<T> toDoubleFunction) {
 return toDoubleFunction;
 }
 public static <T, U> ToIntBiFunction<T, U> asToIntBiFunction(ToIntBiFunction<T, U> toIntBiFunction) {
 return toIntBiFunction;
 }
 public static <T> ToIntFunction<T> asToIntFunction(ToIntFunction<T> ioIntFunction) {
 return ioIntFunction;
 }
 public static <T, U> ToLongBiFunction<T, U> asToLongBiFunction(ToLongBiFunction<T, U> toLongBiFunction) {
 return toLongBiFunction;
 }
 public static <T> ToLongFunction<T> asToLongFunction(ToLongFunction<T> toLongFunction) {
 return toLongFunction;
 }
 public static <T> UnaryOperator<T> asUnaryOperator(UnaryOperator<T> unaryOperator) {
 return unaryOperator;
 }
 private FunctionCastUtil() {
 }
}

Stream.of("A", "", "B").filter(asPredicate(String::isEmpty).negate()).count();