Java: What is the Stream API in Java?

1List<String> names = List.of("Alice", "Bob", "Charlie", "David");
2
3// Filter, map, collect
4List<String> result = names.stream()
5    .filter(name -> name.length() > 3)
6    .map(String::toUpperCase)
7    .sorted()
8    .collect(Collectors.toList());
9// [ALICE, CHARLIE, DAVID]
10
11// Reduce
12int sum = IntStream.range(1, 101).reduce(0, Integer::sum);
13
14// Parallel
15long count = names.parallelStream()
16    .filter(name -> name.startsWith("A"))
17    .count();
18
19// Collectors
20Map<Integer, List<String>> grouped = names.stream()
21    .collect(Collectors.groupingBy(String::length));