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📝 update stream-2 course
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‎README.md‎

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@@ -28,7 +28,7 @@ Java8 改变了我们思考和编码的方式，在这里你可以学习到 Java
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|第 6 课 | [默认方法的妙用](https://github.com/biezhi/learn-java8/blob/master/java8-default-methods/README.md) | [网易云课堂](http://study.163.com/course/courseLearn.htm?courseId=1005047049&utm_campaign=commission&utm_source=cp-400000000397038&utm_medium=share#/learn/video?lessonId=1051518175&courseId=1005047049) ¦ [哔哩哔哩](https://www.bilibili.com/video/av19287893/index_6.html#page=6) ¦ [Youtube](https://youtu.be/sAuEnkWezDM) | [default-method](https://github.com/biezhi/learn-java8/tree/master/java8-default-methods/src/main/java/io/github/biezhi/java8/defaultmethods) |
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|第 7 课 | [干掉空指针之 Optional](https://github.com/biezhi/learn-java8/blob/master/java8-optional/README.md) | [网易云课堂](http://study.163.com/course/courseLearn.htm?courseId=1005047049&utm_campaign=commission&utm_source=cp-400000000397038&utm_medium=share#/learn/video?lessonId=1051511464&courseId=1005047049) ¦ [哔哩哔哩](https://www.bilibili.com/video/av19287893/index_7.html#page=7) ¦ [Youtube](https://youtu.be/br4kqCXPB9A) | [optional](https://github.com/biezhi/learn-java8/tree/master/java8-default-methods/src/main/java/io/github/biezhi/java8/optional) |
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|第 8 课 | [理解 Stream](https://github.com/biezhi/learn-java8/blob/master/java8-stream/README.md) | [网易云课堂](http://study.163.com/course/courseLearn.htm?courseId=1005047049&utm_campaign=commission&utm_source=cp-400000000397038&utm_medium=share#/learn/video?lessonId=1051555343&courseId=1005047049) ¦ [哔哩哔哩](https://www.bilibili.com/video/av19287893/index_8.html#page=8) ¦ [Youtube](https://youtu.be/NB9mGlNMl-w) | [stream](https://github.com/biezhi/learn-java8/tree/master/java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson1) |
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|第 9 课 | Stream API（上）| 网易云课堂 ¦ 哔哩哔哩 ¦ Youtube | |
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|第 9 课 | [Stream API（上）](https://github.com/biezhi/learn-java8/blob/master/java8-stream/README.md#%E4%BD%BF%E7%94%A8%E6%B5%81) | 网易云课堂 ¦ [哔哩哔哩](https://www.bilibili.com/video/av19287893/index_9.html#page=9) ¦ [Youtube](https://youtu.be/mGwFJERNzmY) | [stream](https://github.com/biezhi/learn-java8/blob/master/java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2) |
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|第 10 课 | Stream API（下）| 网易云课堂 ¦ 哔哩哔哩 ¦ Youtube | |
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|第 11 课 | 新的日期时间 API | 网易云课堂 ¦ 哔哩哔哩 ¦ Youtube | |
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|第 12 课 | 并发增强 | 网易云课堂 ¦ 哔哩哔哩 ¦ Youtube | |

‎java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2/Example1.java‎

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package io.github.biezhi.java8.stream.lesson2;
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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Stream;
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/**
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* 创建流
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* <p>
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public class Example1 {
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public static void main(String[] args) {
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List<String> list = Arrays.asList("hello", "world");
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Stream<String> stream = list.stream();
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Stream<String> stringStream = Arrays.stream(new String[]{"hello", "world"});
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Stream<String> stream1 = Stream.of("hello", "world");
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}
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}

‎java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2/Example2.java‎

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import io.github.biezhi.java8.stream.Project;
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import java.util.List;
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import java.util.stream.Collectors;
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import java.util.stream.Stream;
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/**
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* 筛选元素
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public static void main(String[] args) {
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List<Project> projects = Project.buildData();
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List<Project> collect = projects.stream()
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.filter(project -> project.getStars() > 1000)
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.collect(Collectors.toList());
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// distinct
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Stream<Integer> numbers = Stream.of(1, 2, 3, 3, 2, 4);
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numbers.distinct().limit(3).forEach(n -> System.out.println(n));
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System.out.println("===================");
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Stream.of(1, 2, 3, 3, 2, 4).skip(4).forEach(n -> System.out.println(n));
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}
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}

‎java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2/Example3.java‎

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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Collectors;
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/**
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* 映射
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public static void main(String[] args) {
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List<String> words = Arrays.asList("Java 8", "Lambdas", "In", "Action");
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words.stream()
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.map(word -> word.length())
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.collect(Collectors.toList())
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.forEach(i -> System.out.println(i));
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}
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}

‎java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2/Example4.java‎

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import java.util.Arrays;
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import java.util.List;
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import java.util.stream.Collectors;
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/**
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* 扁平流 flatMap
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public static void main(String[] args) {
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List<String> list = Arrays.asList("I am a boy", "I love the girl", "But the girl loves another girl");
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list.stream()
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.map(word -> word.split(" ")) // Stream<String>
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.flatMap(Arrays::stream)
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.distinct()
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.collect(Collectors.toList());
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}
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}

‎java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2/Example5.java‎

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public static void main(String[] args) {
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List<Project> projects = Project.buildData();
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boolean hasBiezhi = projects.stream()
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.anyMatch(p -> p.getAuthor().equals("biezhi"));
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System.out.println(hasBiezhi);
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System.out.println(projects.stream()
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.allMatch(p -> p.getAuthor().equals("biezhi")));
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System.out.println(projects.stream()
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.noneMatch(p -> p.getAuthor().equals("biezhi")));
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System.out.println(projects.stream().findAny().get());
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System.out.println(projects.stream().findFirst().get());
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}
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}

‎java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2/Example6.java‎

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for (int x : numbers) {
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sum += x;
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}
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System.out.println(sum);
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Integer reduce = numbers.stream()
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.reduce(0, (a, b) -> a + b);
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System.out.println(reduce);
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}
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}

‎java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2/Example7.java‎

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package io.github.biezhi.java8.stream.lesson2;
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import io.github.biezhi.java8.stream.Project;
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import java.util.List;
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import java.util.OptionalInt;
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/**
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* 数值流
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* <p>
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public class Example7 {
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public static void main(String[] args) {
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List<Project> projects = Project.buildData();
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OptionalInt max = projects.stream()
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.mapToInt(p -> p.getStars())
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.max();
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System.out.println(max.getAsInt());
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}
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}

‎java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2/Quiz1.java‎

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package io.github.biezhi.java8.stream.lesson2;
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import lombok.AllArgsConstructor;
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import java.util.stream.Stream;
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/**
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* 3. 斐波纳契元组序列
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* <p>
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*/
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public class Quiz1 {
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public static void main(String[] args) {
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@AllArgsConstructor
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static class Tuple{
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int first;
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int second;
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}
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public static void main(String[] args) {
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// tuple = (0, 1)
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// next [0] = prev tuple [1]
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// next [1] = prev (tuple [0] + tuple[1])
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Stream.iterate(new Tuple(0, 1), tuple -> new Tuple(tuple.second, tuple.first + tuple.second))
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.limit(20)
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.forEach(tuple -> System.out.println("("+ tuple.first +","+ tuple.second +")"));
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}
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}

‎java8-stream/src/main/java/io/github/biezhi/java8/stream/lesson2/Quiz2.java‎

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import java.util.ArrayList;
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import java.util.List;
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import java.util.stream.Collectors;
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/**
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* 1. 你将如何利用流来筛选前两个Java项目呢？
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public class Quiz2 {
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public static void main(String[] args) {
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List<Project> projects = new ArrayList<>();
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List<Project> projects = Project.buildData();
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System.out.println(projects.stream().map(Project::getName).limit(2).collect(Collectors.toList()));
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}
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}

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