Which statement is true about the single abstract method of the java.util.function.Function interface?

Question

Options

• AIt accepts one argument and returns void.
• BIt accepts one argument and returns boolean.
• CIt accepts one argument and always produces a result of the same type as the argument.
• DIt accepts an argument and produces a result of any data type.

• A
  5% (3)
• B
  13% (7)
• C
  4% (2)
• D
  79% (44)

Explanation

Function<T, R> declares R apply(T t) - two independent type parameters mean the input and output can be completely different types (e.g., Function<String, Integer> parses a String into an Integer). That's why D is correct: no restriction ties the return type to the argument type.

Why the distractors fail:

• A describes Consumer<T> - same single argument, but accept() returns void.
• B describes Predicate<T> - same single argument, but test() returns boolean.
• C is the trickiest distractor: Function can return the same type (e.g., Function<String, String>), but it is not required to - the type parameters T and R are independent, so this constraint simply doesn't exist.

Memory tip: Map the four core functional interfaces to their signatures - Supplier gives, Consumer takes, Predicate tests (→ boolean), and Function transforms (T → R, anything to anything).

No community discussion yet for this question.