What are some examples of using the map function in Java 8 Stream API?

Can you explain the map function in Java 8 Stream API with examples?

Sure! The map function in Java 8 Stream API is used to transform each element of a stream. For example, if you have a list of integers and you want to square each number, you can use map like this:

List<Integer> numbers = Arrays.asList(1, 2, 3, 4);
List<Integer> squares = numbers.stream().map(n -> n * n).collect(Collectors.toList());

That's great! Can you give me another example using a list of strings?

Absolutely! If you have a list of strings and you want to convert them to uppercase, you can do it like this:

List<String> words = Arrays.asList("hello", "world");
List<String> uppercased = words.stream().map(String::toUpperCase).collect(Collectors.toList());

What if I want to filter the list before mapping?

You can chain the filter method before map. For instance, if you want to square only the even numbers:

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