Functional Interface Specializations in Java - Quiz
Total: 21 questions
1. Enumerate the most commonly used functional interfaces.
Enumerate the most commonly used functional interfaces.
Predicate, Consumer, Supplier, Function and UnaryOperator.
2. The purpose of binary specializations of Predicate, Consumer, Function and UnaryOperator common interfaces.
The purpose of binary specializations of Predicate, Consumer, Function and UnaryOperator common interfaces.
The Predicate, Consumer, Function and UnaryOperator functional interfaces represent an operation that takes one argument. Their binary versions take two arguments called. They have the same semantics, the only difference is the number of arguments.
3. The binary version of the Consumer interface.
The binary version of the Consumer interface.
BiConsumer<T, U>
4. The binary version of the Function interface.
The binary version of the Function interface.
BiFunction<T, U, R>
5. The binary version of the Predicate interface.
The binary version of the Predicate interface.
BiPredicate<T, U>
6. The binary version of the UnaryOperator interface.
The binary version of the UnaryOperator interface.
BinaryOperator<T>
7. The purpose of primitive specializations of Predicate, Consumer, Function, Supplier and UnaryOperator common interfaces.
The purpose of primitive specializations of Predicate, Consumer, Function, Supplier and UnaryOperator common interfaces.
Primitive specializations give the possibility to avoid autoboxing operations when the inputs or outputs are primitives.
8. Rewrite the example using primitive specialization:
Consumer<Integer> ic = i -> System.out.println(++i);
ic.accept(8);
ic.accept(9);
Rewrite the example using primitive specialization:
Consumer<Integer> ic = i -> System.out.println(++i);
ic.accept(8);
ic.accept(9);IntConsumer ic = i -> System.out.println(++i);
ic.accept(8);
ic.accept(9);
9. Enumerate primitive specializations of Consumer functional interface.
Enumerate primitive specializations of Consumer functional interface.
IntConsumer
LongConsumer
DoubleConsumer
10. Enumerate consuming primitive specializations of the Function functional interface.
Enumerate consuming primitive specializations of the Function functional interface.
IntFunction<R>
LongFunction<R>
DoubleFunction<R>
11. Enumerate producing primitive specializations of the Function functional interface.
Enumerate producing primitive specializations of the Function functional interface.
ToIntFunction<T>
ToLongFunction<T>
ToDoubleFunction<T>
12. Enumerate producing/consuming primitive specializations of the Function functional interface.
Enumerate producing/consuming primitive specializations of the Function functional interface.
IntToDoubleFunction
IntToLongFunction
LongToDoubleFunction
LongToIntFunction
DoubleToIntFunction
DoubleToLongFunction
13. Enumerate primitive specializations of Supplier functional interface.
Enumerate primitive specializations of Supplier functional interface.
BooleanSupplier
IntSupplier
LongSupplier
DoubleSupplier
14. Enumerate primitive specializations of UnaryOperator functional interface.
Enumerate primitive specializations of UnaryOperator functional interface.
IntUnaryOperator
LongUnaryOperator
DoubleUnaryOperator
15. Enumerate primitive specializations of BinaryOperator functional interface.
Enumerate primitive specializations of BinaryOperator functional interface.
IntBinaryOperator
LongBinaryOperator
DoubleBinaryOperator
16. Enumerate primitive specializations of BiConsumer functional interface.
Enumerate primitive specializations of BiConsumer functional interface.
ObjIntConsumer<T>
ObjLongConsumer<T>
ObjDoubleConsumer<T>
17. Enumerate primitive specializations of BiFunction functional interface.
Enumerate primitive specializations of BiFunction functional interface.
ToIntBiFunction<T, U>
ToLongBiFunction<T, U>
ToDoubleBiFunction<T, U>
18. Enumerate primitive specializations of the Predicate functional interface. Does BiPredicate have a primitive version?
Enumerate primitive specializations of the Predicate functional interface. Does BiPredicate have a primitive version?
IntPredicate — boolean test(int)
LongPredicate — boolean test(long)
DoublePredicate — boolean test(double)
BiPredicate has no primitive specializations: there is no IntBiPredicate or ObjIntPredicate in the package.
19. How do you reconstruct the signature of a java.util.function interface from its name?
How do you reconstruct the signature of a java.util.function interface from its name?
The names follow a strict pattern:
Int / Long / Double prefix — the input type: IntPredicate — boolean test(int).
To + type — the return type: ToIntFunction<T> — int applyAsInt(T).
type + To + type — both input and output are primitive: IntToDoubleFunction — double applyAsDouble(int).
Obj + type — an object plus a primitive: ObjIntConsumer<T> — void accept(T, int).
Bi prefix — two object arguments: BiFunction<T, U, R> — R apply(T, U).
UnaryOperator / BinaryOperator — all types are the same: IntBinaryOperator — int applyAsInt(int, int).
When the result is primitive, the method name gets the As + type suffix: applyAsInt, getAsDouble. The test() and accept() methods have no suffix — their return types are already fixed.
20. Which functional interfaces do the Stream and IntStream methods expect: mapToInt(), map(), mapToObj(), filter(), forEach(), reduce()?
Which functional interfaces do the Stream and IntStream methods expect: mapToInt(), map(), mapToObj(), filter(), forEach(), reduce()?
Stream<T>.mapToInt() — ToIntFunction<T>, switches to an IntStream.
IntStream.map() — IntUnaryOperator.
IntStream.mapToObj() — IntFunction<R>, switches back to a Stream<R>.
IntStream.filter() — IntPredicate.
IntStream.forEach() — IntConsumer.
IntStream.reduce() — IntBinaryOperator.
Also: Map.forEach() expects a BiConsumer<K, V>, Map.merge() a BiFunction<V, V, V>, and List.replaceAll() a UnaryOperator<E>.
21. Which primitive types have specializations, and do those specializations inherit the generic interfaces?
Which primitive types have specializations, and do those specializations inherit the generic interfaces?
Specializations exist only for int, long and double (plus BooleanSupplier for boolean). There are no interfaces for float, byte, short or char — the int and double versions are used instead, relying on widening conversion.
Primitive specializations do not inherit the generic interfaces: IntPredicate is not a subtype of Predicate<Integer>, and IntBinaryOperator is not a subtype of BiFunction. They are unrelated types and cannot be assigned to each other.