@Test
public void reduce() {
IntStream stream = IntStream.of(1, 2, 3, 4);
assertEquals(10, stream.reduce(0, (a, b) -> a + b));
Stream<Integer> stream2 = Arrays.asList(1, 2, 3, 4).stream();
stream2.reduce(0, (a, b) -> a + b);
// obviously the operations can be more complex :)
Stream<Integer> stream3 = Arrays.asList(1, 2, 3, 4).stream();
// reduce is a superset of map :D
System.err.println(
stream3.reduce(
new ArrayList<Integer>(),
(List<Integer> a, Integer b) -> {
a.add(b);
return a;
},
(a, b) -> {
List<Integer> c = new ArrayList<>(a);
c.addAll(b);
return c;
}));
}