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How to implement ToLongFunction using lambda expression in Java?
ToLongFunction<T> is a functional interface defined in java.util.function package. This functional interface accepts a reference type as input and produces a long-valued result. ToLongFunction<T> interface can be used as an assignment target for a lambda expression or method reference. It contains only one abstract method: applyAsLong().
Syntax
@FunctionalInterface
interface ToLongFunction<T> {
long applyAsLong(T value);
}Example
import java.util.*;
import java.util.function.ToLongFunction;
public class ToLongFunctionTest {
public static void main(String args[]) {
List<String> list = new ArrayList<String>();
list.add("11");
list.add("22");
list.add("33");
list.add("44");
list.add("55");
ToLongFunction<String> function = (String item) -> Long.valueOf(item); // lambda expression
list.stream().mapToLong(function).forEach(System.out::println);
}
}Output
11 22 33 44 55
Updated on: 14-Jul-2020
183 Views
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