@SuppressWarnings("unchecked")
@Override
default Tuple2<Seq<T>, Seq<T>> span(Predicate<? super T> predicate) {
Objects.requireNonNull(predicate, "predicate is null");
if (isEmpty()) {
return Tuple.of(Stream.empty(), Stream.empty());
} else {
return (Tuple2<Seq<T>, Seq<T>>) traverse().span(predicate);
}
}
static <T> Stream<T> levelOrder(Tree<T> tree) {
Stream<T> result = Stream.empty();
final java.util.Queue<Tree<T>> queue = new java.util.LinkedList<>();
queue.add(tree);
while (!queue.isEmpty()) {
final Tree<T> next = queue.remove();
result = result.prepend(next.getValue());
queue.addAll(next.getChildren().toJavaList());
}
return result.reverse();
}
static <T> Stream<T> inOrder(Tree<T> tree) {
if (tree.isLeaf()) {
return Stream.of(tree.getValue());
} else {
final List<Node<T>> children = tree.getChildren();
return children
.tail()
.foldLeft(Stream.<T>empty(), (acc, child) -> acc.appendAll(inOrder(child)))
.prepend(tree.getValue())
.prependAll(inOrder(children.head()));
}
}
public static void main(String... args) {
/*
-------------------------------------------------------------------------
From obj to ...
-------------------------------------------------------------------------
*/
Stream<String> streamOfStrings = Stream.of("un", "deux", "trois");
Function<String, StringBuilder> function = StringBuilder::new;
streamOfStrings.map(function) /*.forEach(System.out::println)*/;
streamOfStrings = Stream.of("un", "deux", "trois");
ToIntFunction<String> toIntFunction = String::length;
IntStream streamOfInts = streamOfStrings.mapToInt(toIntFunction);
streamOfStrings = Stream.of("un", "deux", "trois");
ToDoubleFunction<String> toDoubleFunction = String::length;
DoubleStream streamOfDoubles = streamOfStrings.mapToDouble(toDoubleFunction);
streamOfStrings = Stream.of("un", "deux", "trois");
ToLongFunction<String> toLongFunction = String::length;
LongStream streamOfLongs = streamOfStrings.mapToLong(toLongFunction);
/*
-------------------------------------------------------------------------
From int to ...
-------------------------------------------------------------------------
*/
IntUnaryOperator plusplus = i -> i++;
IntStream.of(1, 2, 3).map(plusplus)
/*.forEach(x->System.out.println(x))*/ ;
IntFunction<String> intFunction = i -> "" + i;
IntStream.of(1, 2, 3).mapToObj(intFunction)
/*.forEach(System.out::println)*/ ;
IntToDoubleFunction itdf = i -> i;
IntStream.of(1, 2, 3).mapToDouble(itdf)
/*.forEach(System.out::println)*/ ;
IntToLongFunction itlf = i -> i;
IntStream.of(1, 2, 3).mapToLong(itlf)
/*.forEach(System.out::println)*/ ;
/*
-------------------------------------------------------------------------
From long to ...
-------------------------------------------------------------------------
*/
LongUnaryOperator times = l -> l * l;
LongStream.of(1L, 2L, 3L).map(times)
/*.forEach(System.out::println)*/ ;
LongFunction<String> lf = l -> "toto";
LongStream.of(1L, 2L, 3L).mapToObj(lf);
/*
-------------------------------------------------------------------------
From double to ...
-------------------------------------------------------------------------
*/
DoubleToIntFunction dtif = d -> (int) d;
DoubleStream.of(1.3, 1.5, 1.6).mapToInt(dtif).forEach(System.out::println);
}
public static void main(String[] args) {
Map<Integer, HashSet<String>> withSet =
Stream.of("jon", "andrew", "harvey", "bil")
.collect(Collectors.groupingBy(String::length, HashSet::new));
out.println(withSet);
}
@Override
default Seq<T> takeRight(int n) {
if (isEmpty()) {
return Stream.empty();
} else {
return traverse().takeRight(n);
}
}
@Override
default Seq<T> dropRight(int n) {
if (n >= length()) {
return Stream.empty();
} else {
return traverse().dropRight(n);
}
}
@Override
default Seq<T> filter(Predicate<? super T> predicate) {
Objects.requireNonNull(predicate, "predicate is null");
if (isEmpty()) {
return Stream.empty();
} else {
return traverse().filter(predicate);
}
}
@Override
default <U> Seq<T> distinctBy(Function<? super T, ? extends U> keyExtractor) {
Objects.requireNonNull(keyExtractor, "keyExtractor is null");
if (isEmpty()) {
return Stream.empty();
} else {
return traverse().distinctBy(keyExtractor);
}
}
@Override
default Seq<T> distinctBy(Comparator<? super T> comparator) {
Objects.requireNonNull(comparator, "comparator is null");
if (isEmpty()) {
return Stream.empty();
} else {
return traverse().distinctBy(comparator);
}
}
/**
* Traverses the Tree in a specific order.
*
* @param order the tree traversal order
* @return A List containing all elements of this tree, which is List if this tree is empty.
* @throws java.lang.NullPointerException if order is null
*/
default Seq<T> traverse(Order order) {
Objects.requireNonNull(order, "order is null");
if (isEmpty()) {
return Stream.empty();
} else {
switch (order) {
case PRE_ORDER:
return Traversal.preOrder(this);
case IN_ORDER:
return Traversal.inOrder(this);
case POST_ORDER:
return Traversal.postOrder(this);
case LEVEL_ORDER:
return Traversal.levelOrder(this);
default:
throw new IllegalStateException("Unknown order: " + order.name());
}
}
}
static <T> Stream<T> postOrder(Tree<T> tree) {
return tree.getChildren()
.foldLeft(Stream.<T>empty(), (acc, child) -> acc.appendAll(postOrder(child)))
.append(tree.getValue());
}
static <T> Stream<T> preOrder(Tree<T> tree) {
return tree.getChildren()
.foldLeft(Stream.of(tree.getValue()), (acc, child) -> acc.appendAll(preOrder(child)));
}