Java 8 | DoubleToLongFunction Interface in Java with Examples Last Updated : 28 Sep, 2018 Comments Improve Suggest changes Like Article Like Report The DoubleToLongFunction Interface is a part of the java.util.function package which has been introduced since Java 8, to implement functional programming in Java. It represents a function which takes in a double-valued argument and gives an long-valued result. The lambda expression assigned to an object of DoubleToLongFunction type is used to define its applyAsLong() which eventually applies the given operation on its only argument. It is similar to using an object of type Function<Double, Long>. The DoubleToLongFunction interface has only one function: 1. applyAsLong() : This method accepts a double-valued argument and gives an long-valued result. Syntax: long applyAsLong(double value) Parameters: This method takes in one parameter value which is the double-valued argument. Returns: This method returns an long-valued result. Below is the code to illustrate applyAsLong() method: Program Java // Java Program to demonstrate // DoubleToLongFunction's applyAsLong() method import java.util.function.DoubleToLongFunction; public class Main { public static void main(String args[]) { // Declare the DoubleToLongFunction DoubleToLongFunction truncate = a -> (long)a; // Apply the function to get the result as long // using applyAsLong() System.out.println(truncate.applyAsLong(10.6)); } } Output: 10 Comment More infoAdvertise with us Next Article Java 8 | DoubleToLongFunction Interface in Java with Examples P psil123 Follow Improve Article Tags : Misc Java Java - util package java-basics Java 8 +1 More Practice Tags : JavaMisc Similar Reads Java 8 | DoubleToIntFunction Interface in Java with Example The DoubleToIntFunction Interface is a part of the java.util.function package which has been introduced since Java 8, to implement functional programming in Java. 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