private static final String[] strs = new String[]{"apple", "pear", "orange"};

private List<String> stringList = new ArrayList<>();

public void init() {

stringList.add("phone");

stringList.add("phoneb");

stringList.add("");

stringList.add("phoneb");

stringList.add("phonec");

stringList.add("penc");

}

public void creation() {

Stream<String> streamEmpty = Stream.empty(); // to avoid returning null

Collection<String> collection = Arrays.asList("ab", "cd", "ef");

Stream<String> stream1 = collection.stream();

Stream<String> stream2 = Stream.of("sd", "iw", "me");

Stream<String> stream3 = Stream.<String>builder().add("tom").add("saul").add("jimmy").build();

Stream<String> stream4 = Stream.generate(() -> "repeat").limit(5);

IntStream intStream = IntStream.range(1,5); // 1~4

System.out.println(intStream.count());

LongStream longStream = LongStream.rangeClosed(1,5); // include 5

System.out.println(longStream.count());

}

public void fromString() {

Stream<String> stream = Arrays.stream(strs);

Stream<String> streamb = Stream.of("jack", "tom", "zero");

Stream<String> streamc = stringList.stream();

//parallelStream() allows to run method doWork() in parallel for every element of the stream

Stream<String> streamPa = stringList.parallelStream();

System.out.println("distinct elem in stringList is: " + streamPa.distinct().count());

}

public void operation() {

// iterate

boolean isPhonecExist = stringList.stream().anyMatch(element -> element.contains("phonec"));

System.out.println(isPhonecExist);

// filter

Stream<String> streamFilterd = stringList.stream().filter(element -> element.contains("c"));

System.out.println(streamFilterd.count());

// map

Stream<Integer> strsLength = stringList.stream().map(element -> element.length());

System.out.println(strsLength.toArray()[0]);

// flatmap

List<Detail> details = new ArrayList<>();

details.add(new Detail());

details.add(new Detail());

Stream<String> logos = details.stream().flatMap(detail -> detail.getParts().stream());

// reduce

List<Integer> nums = Arrays.asList(23,3,93,64,34);

Integer sum = nums.stream().reduce(1000, (a,b) -> a + b);

System.out.println(sum);

// collect

List<String> logoStrs = logos.map( e -> e.toUpperCase())

.collect(Collectors.toList());

System.out.println(logoStrs.get(1));

// reference to the instance method

long count = stringList.stream().filter(String::isEmpty).count();

System.out.println(count);

}

public void testOptional() {

Optional<List<String>> detailOptional = Optional.ofNullable(new Detail().getParts());

System.out.println(detailOptional.isPresent());

String stringOptional = detailOptional

.map(stringList -> stringList.get(0))

.orElse("empty");

System.out.println(stringOptional);

}

public static void main(String[] args) {

StreamsPrac sp = new StreamsPrac();

sp.init();

sp.testOptional();

}

private class Detail {

public List<String> getParts() {

return parts;

}

private List<String> parts;

public Detail() {

}

public void init() {

if (parts == null) {

parts = new ArrayList<>();

}

this.parts.add("apple");

this.parts.add("huawei");

this.parts.add("vivo");

}

}