Junior — Middle

Which interface implements the filter method in functional programming?

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Answer from AI

In Java, the filter method is used in the Stream API and takes a functional interface Predicate<T> as a parameter. This interface represents a function that accepts an object of type T and returns a boolean value (true or false). The filter method only passes through those stream elements for which the Predicate returns true.

Example:

List<String> names = List.of("Anna", "Bob", "Alice", "Tom");
List<String> filtered = names.stream()
    .filter(name -> name.startsWith("A")) // Predicate<String>
    .collect(Collectors.toList());

System.out.println(filtered); // [Anna, Alice]

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