ToDoubleBiFunction Interface in Java with Examples

The ToDoubleBiFunction 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 two arguments of type T and U and produces a double-valued result.

This functional interface takes in two generics, namely:-

• T: denotes the type of the first input argument to the operation
• U: denotes the type of the second input argument to the operation

The lambda expression assigned to an object of ToDoubleBiFunction type is used to define its applyAsDouble() which eventually applies the given operation on its two arguments. It is similar to using an object of type BiFunction<T, U, Double>.

The ToDoubleBiFunction interface has only one function:

applyAsDouble()

This method accepts two arguments of type T and U and produces a double-valued result.

Syntax:

double applyAsDouble(T t, U u)

Parameters: This method takes in two parameters:

• t– the first input argument
• u– the second input argument

Returns: This method returns a double-valued result.

Below is the code to illustrate applyAsDouble() method:

Program

import java.util.function.ToDoubleBiFunction;

public class Main {
    public static void main(String args[])
    {

        ToDoubleBiFunction<Integer, String>
            ob = (a, b) -> a + Integer.parseInt(b) * 3.2;

        // Using applyAsDouble()
        System.out.println(ob.applyAsDouble(3, "10"));
    }
}

Output:

35.0