List<String> l = new ArrayList(Arrays.asList("one", "two"));
Stream<String> sl = l.stream();
sl.forEach(s -> l.add("three"));

List<String> l = new ArrayList(Arrays.asList("one", "two"));
Stream<String> sl = l.stream();
l.add("three");
sl.forEach(System.out::println);

List<String> l = new CopyOnWriteArrayList<>(Arrays.asList("one", "two"));
Stream<String> sl = l.stream();
sl.forEach(s -> l.add("three"));

List<String> l = new ArrayList(Arrays.asList("one", "two", ……));
class State {
    boolean s;
}
final State state = new State();
Stream<String> sl = l.stream().map(e -> {
    if (state.s)
        return "OK";
    else {
        state.s = true;
        return e;
    } 
});
sl.forEach(System.out::println);

a op b op c op d == (a op b) op (c op d)

List<String> l = Stream.of("a","b","c","b")
        .distinct()
        .collect(Collectors.toList());
System.out.println(l); //[a, b, c]

List<Integer> l = IntStream.range(1,10)
        .filter( i -> i % 2 == 0)
        .boxed()
        .collect(Collectors.toList());
System.out.println(l); //[2, 4, 6, 8]

List<Integer> l = Stream.of('a','b','c')
        .map( c -> c.hashCode())
        .collect(Collectors.toList());
System.out.println(l); //[97, 98, 99]

<R> Stream<R> flatMap(Function<? super T,? extends Stream<? extends R>> mapper)

String poetry = "Where, before me, are the ages that have gone?\n" +
        "And where, behind me, are the coming generations?\n" +
        "I think of heaven and earth, without limit, without end,\n" +
        "And I am all alone and my tears fall down.";
Stream<String> lines = Arrays.stream(poetry.split("\n"));
Stream<String> words = lines.flatMap(line -> Arrays.stream(line.split(" ")));
List<String> l = words.map( w -> {
    if (w.endsWith(",") || w.endsWith(".") || w.endsWith("?"))
        return w.substring(0,w.length() -1).trim().toLowerCase();
    else
        return w.trim().toLowerCase();
}).distinct().sorted().collect(Collectors.toList());
System.out.println(l); //[ages, all, alone, am, and, are, before, behind, coming, down, earth, end, fall, generations, gone, have, heaven, i, limit, me, my, of, tears, that, the, think, where, without]

String[] arr = new String[]{"a","b","c","d"};
Arrays.stream(arr)
        .peek(System.out::println) //a,b,c,d
        .count();

String[] arr = new String[]{"b_123","c+342","b#632","d_123"};
List<String> l  = Arrays.stream(arr)
        .sorted((s1,s2) -> {
            if (s1.charAt(0) == s2.charAt(0))
                return s1.substring(2).compareTo(s2.substring(2));
            else
                return s1.charAt(0) - s2.charAt(0);
        })
        .collect(Collectors.toList());
System.out.println(l); //[b_123, b#632, c+342, d_123]

mapToLong(e -> 1L).sum();

R result = supplier.get();
for (T element : this stream)
    accumulator.accept(result, element);
return result;

List<String> asList = stringStream.collect(ArrayList::new, ArrayList::add,
                                           ArrayList::addAll);
String concat = stringStream.collect(StringBuilder::new, StringBuilder::append,
                                     StringBuilder::append)
                            .toString();

Stream.of(1,2,3,4,5).forEach(System.out::println);

pubic Optional<T> 	reduce(BinaryOperator<T> accumulator)
pubic T 	reduce(T identity, BinaryOperator<T> accumulator)
pubic <U> U 	reduce(U identity, BiFunction<U,? super T,U> accumulator, BinaryOperator<U> combiner)

Optional<Integer> total = Stream.of(1,2,3,4,5).reduce( (x, y) -> x +y);
Integer total2 = Stream.of(1,2,3,4,5).reduce(0, (x, y) -> x +y);

public static <T> Stream<T> 	concat(Stream<? extends T> a, Stream<? extends T> b)

public static <T,C extends Collection<T>> Collector<T,?,C> 	toCollection(Supplier<C> collectionFactory)
public static …… 	toConcurrentMap(……)
public static <T> Collector<T,?,List<T>> 	toList()
public static …… 	toMap(……)
public static <T> Collector<T,?,Set<T>> 	toSet()