The IntToLongFunction 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 an int-valued argument and gives a long-valued result.
The lambda expression assigned to an object of IntToLongFunction 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<Integer, Long> .
The IntToLongFunction interface has only one function:
applyAsLong() : This method accepts an int-valued argument and gives a long-valued result.
long applyAsLong(int value)
Parameters: This method takes in one parameter value which is the int-valued argument.
Returns: This method returns a long-valued result.
Below is the code to illustrate applyAsLong() method: