Java8 Streams stuff

java8streams

public class StreamsTest {
	
	@Test
	public void chapter2Stream1() {
		String contents = "catch,catching,cat,cats,dog,eating";
		String[] splitted = contents.split("[\\ P{ L}] +");
		System.out.println(splitted);
		String[] wordsArray = { "catch", "catching", "cat", "cats", "dog", "eating"};
		Stream<String> stream = Arrays.stream(wordsArray, 1, wordsArray.length);
		stream.forEach(System.out::println);
		System.out.println(wordsArray);
		Stream<String> words = Stream.of(wordsArray);
		long c = words.filter(s -> s.contains("at")).count();
		System.out.println(c);
	}
	
	/*
	 * Skip the first element of array when creating stream
	 */
	@Test
	public void Chapter2StreamFromPartOfList() {
		String[] wordsArray = { "catch", "catching", "cat", "cats", "dog", "eating"};
		Stream<String> stream = Arrays.stream(wordsArray, 1, wordsArray.length);
		stream.forEach(System.out::println);
	}
	
	@Test
	public void infiniteStream() {
		Stream <Double> echos = Stream.generate(Math::random);
		//echos.forEach(System.out::println);		
	}
	
	@Test
	public void infiniteSequence() {
		Stream <BigInteger> integers = Stream.iterate(BigInteger.ZERO, n -> n.add( BigInteger.valueOf(2)));
		// just get first 500 values
		integers.limit(5).forEach(System.out::println);
	}
	
	@Test
	public void mapAStream() {
		CsvRow[] rows = { new CsvRow("huzi", "chipin", "4"), new CsvRow("tigger", "jack russell", "12")};
		Stream<CsvRow> stream = Arrays.stream(rows);
		Stream<Dog> dogs = stream.map(row -> new Dog(row.get(0), row.get(1)));
		Map<String, String> collectedDogs = dogs.collect(Collectors.toMap((Dog d) -> d.getName(), (Dog d) -> d.getType()));
		//Stream<Pet> petStream = stream.map(row -> new Pet(row.get(0), row.get(1)));
		//Map<String, String> collectedPets = petStream.collect(Collectors.toMap((Pet p) -> p.getName(), (Pet p) -> p.getType()));
		System.out.println(collectedDogs);
		//sSystem.out.println(collectedPets);
	}
	
	@Test 
	public void streamOfStreamsWithMap() {
		List<String> words = new ArrayList<>();
		words.add("james");
		words.add("john");
		Stream<Stream<Character>> result = words.stream().map(w -> characterStream(w));
		List<Stream<Character>> collect = result.collect(Collectors.toList());
		collect.forEach(str -> System.out.println(str.collect(Collectors.toList())));
	}
	
	@Test 
	public void streamOfStreamsWithFlatMap() {
		List<String> words = new ArrayList<>();
		words.add("james");
		words.add("john");
		Stream<Character> flatMap = words.stream().flatMap(w -> characterStream(w));
		List<Character> collectedChars = flatMap.collect(Collectors.toList());
		collectedChars.forEach(System.out::print);
		Stream<String> sIter = Stream.iterate("str", s -> s + "s");
		List<String> collect = sIter.limit(5).collect(Collectors.toList());
		System.out.println(collect);
		
	}

	public static Stream<Character> characterStream(String s) {
		List<Character> result = new ArrayList<>();
		for (char c : s.toCharArray())
			result.add(c);
		return result.stream();
	}

	/*
	 * Peeking to see elements as they go though the pipeline
	 */
	@Test
	public void peeking() {
		Stream.of("one", "two", "three", "four").filter(e -> e.length() > 3)
				.peek(e -> System.out.println("Filtered value: " + e))
				.map(String::toUpperCase)
				.peek(e -> System.out.println("Mapped value: " + e))
				.collect(Collectors.toList());

	}
	
	
	
	
}