Stream method maps objects to double values and returns a DoubleStream. The method receives an object that implements the functional interface ToDoubleFunction (package java. util. function).

mapToDouble()

Explanation:

The method being described is the mapToDouble() method. This is a method that is built into a pre-defined Java package. This function takes in another function as a parameter to perform on a set of values. This is why the stream().mapToDouble() function is usually called on a list of values. The outputs will be a list of Double type values. An example of this would be the following code which takes in a list of strings and divides their length by 2 and maps them as Doubles. Which will output a list of double values.

       list.stream().mapToDouble(str -> str.length() / 2)

                    .forEach(System.out::println);