package stream;

import java.nio.file.Files;

import java.nio.file.Paths;

import java.util.ArrayList;

import java.util.List;

import java.util.Optional;

import java.util.function.Predicate;

import java.util.stream.Stream;

public final class StreamTest {

private StreamTest() {

}

public static void main(String[] args) throws Exception {

// 基于数组创建Stream

Stream<String> stream = Stream.of("Sam", "Jack", "Tom", "James", "Lucy", "David", "Betty");

stream = Stream.empty(); // 创建空的Stream

System.out.println(stream.getClass().getCanonicalName());

Stream<Double> randomGen = Stream.generate(Math::random); // 基于生成器创建的Stream

randomGen.limit(10).forEach(System.out::println);

try (Stream<String> lines = Files.lines(Paths.get("pom.xml"))) {

lines.limit(1).forEach(System.out::println);

}

stream = Stream.of("Sam", "Jack", "Tom", "James", "Lucy", "David", "Betty");

Predicate<String> lenPredicate = str -> str.length() > 3;

stream = stream.filter(lenPredicate); // filter方法接受一个Predicate类型的函数

stream.map(s -> "Hello " + s).forEach(System.out::println); // 使用map函数对集合进行转化

stream = Stream.of("Sam", "Jack", "Tom", "James", "Lucy", "David", "Betty");

Stream<Character> charStream = stream.flatMap(w -> charStream(w)); // 将多个流进行平铺

charStream.forEach(System.out::println);

stream = Stream.of("Sam", "Jack", "Tom", "James", "Lucy", "David", "Betty");

Optional<String> maxLengthName =

stream.max((str1, str2) -> Integer.compare(str1.length(), str2.length()));

System.out.println(">>>> max length name:" + maxLengthName.get());

stream = Stream.of("Sam", "Jack", "Tom", "James", "Lucy", "David", "Betty");

Optional<String> startsWithJ = stream.filter(str -> str.startsWith("J")).findFirst();

System.out.println(">>>> first with J:" + startsWithJ.get());

stream = Stream.of("Sam", "Jack", "Tom", "James", "Lucy", "David", "Betty");

startsWithJ = stream.parallel().filter(str -> str.startsWith("J")).findAny();

System.out.println(">>>> any with J:" + startsWithJ.get());

startsWithJ.ifPresent(System.out::println); // 如果不为null,那么可以指定处理此值的函数

Optional<String> withHello = startsWithJ.map(s -> String.format("Hello %s", s));

System.out.println(withHello.orElse(""));

stream = Stream.of("Sam", "Jack", "Tom", "James", "Lucy", "David", "Betty");

boolean hasStartsWithJ = stream.parallel().anyMatch(s -> s.startsWith("J"));

System.out.println(">>>> starts with j:" + hasStartsWithJ);

}

public static Stream<Character> charStream(String s) {

List<Character> result = new ArrayList<>();

for (char c : s.toCharArray()) {

result.add(c);

}

return result.stream();

}

}