What is the LongFunction interface in Java?

Overview

LongFunction is a functional interface that accepts one argument of type long and returns back a result. The interface contains one method, apply.

The LongFunction interface is defined in the java.util.function package. To import the LongFunction interface, check the following import statement.

import java.util.function.LongFunction;

apply(long value) method

This method applies the functionality to the given argument of type long. This is the functional method of the interface.

Syntax

R apply(long value);

Parameters

  • long value: This is the function argument of type long.

Return type

The method returns the function result.

Code

import java.util.function.LongFunction;
public class Main{
    public static void main(String[] args) {
        LongFunction<String> stringLongFunction = (d) -> String.format("The passed value is %s", d);
        long l = 100;
        // calling apply method of the LongFunction
        System.out.println(stringLongFunction.apply(l));
    }
}

Explanation

  • Line 1: We import the LongFunction interface.
  • Line 5: We define an implementation of the LongFunction interface called stringLongFunction that returns a string.
  • Line 6: We define a long value called l.
  • Line 9: We print the result of using the apply() method passing l as an argument.

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