How do I use map, filter, and reduce in Java 8?

How do I use map, filter, and reduce in Java 8?

In Java 8, you can use the Stream API to apply map, filter, and reduce operations on collections. Would you like an example?

Yes, please provide an example using a list of integers.

Sure! Here's a simple example:

List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
int sum = numbers.stream()
                 .filter(n -> n % 2 == 0) // filter even numbers
                 .map(n -> n * 2) // double the even numbers
                 .reduce(0, Integer::sum); // sum them up

This code filters even numbers, doubles them, and then sums them.

What if I want to collect the results into a new list instead of summing them?

You can use the collect method instead of reduce. Here's how:

List<Integer> doubledEvens = numbers.stream()
                                     .filter(n -> n % 2 == 0)
                                     .map(n -> n * 2)
                                     .collect(Collectors.toList());

This will give you a list of doubled even numbers.