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[add] add examples of lambda to show usage · j7fantasy/java-learning@3a582e2 · GitHub

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[add] add examples of lambda to show usage
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‎README.md‎

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**博客目录**
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- [javase](/blogs/javase)
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- [Java SE](/blogs/javase)
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- [java基础巩固笔记(1)-反射.md](/blogs/javase/java基础巩固笔记(1)-反射.md)
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- [java基础巩固笔记(2)-泛型.md](/blogs/javase/java基础巩固笔记(2)-泛型.md)
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- [java基础巩固笔记(3)-类加载器.md](/blogs/javase/java基础巩固笔记(3)-类加载器.md)
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- [java基础巩固笔记(5)-多线程之共享数据.md](/blogs/javase/java基础巩固笔记(5)-多线程之共享数据.md)
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- [java基础巩固笔记(5)-多线程之线程并发库.md](/blogs/javase/java基础巩固笔记(5)-多线程之线程并发库.md)
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- [java基础巩固笔记(6)-注解.md](/blogs/javase/java基础巩固笔记(6)-注解.md)
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- [javaweb](/blogs/javaweb)
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- [Java Web](/blogs/javaweb)
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- [javaweb入门笔记(1)-Tomcat.md](/blogs/javaweb/javaweb入门笔记(1)-Tomcat.md)
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- [javaweb入门笔记(2)-http入门.md](/blogs/javaweb/javaweb入门笔记(2)-http入门.md)
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- [javaweb入门笔记(3)-Servlet.md](/blogs/javaweb/javaweb入门笔记(3)-Servlet.md)
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* [ ] 容器类部分使用模块 java-container
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* [ ] IO 部分使用模块 java-io
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* [ ] Java 虚拟机相关部分使用模块 java-jvm
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* [ ] Java 8 新特性使用模块 java8
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* [ ] Java 8 新特性使用模块 java8(正在进行)
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-----

‎java8/README.md‎

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# Java 8 新特性
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《Java 8 In Action》一书
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阅读《Java 8 in Action》一书的简单整理
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源码参考了 **java8/Java8InAction**:[https://github.com/java8/Java8InAction](https://github.com/java8/Java8InAction)
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## lambda 表达式
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- FilteringApples: 传递代码的例子,展示方法引用和Lambda
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## steam API
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‎java8/src/main/java/com/brianway/learning/java8/lambda/ExecuteAround.java‎

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package com.brianway.learning.java8.lambda;
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import java.io.BufferedReader;
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import java.io.FileReader;
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import java.io.IOException;
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/**
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* Lambda实践: 环绕执行模式
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* 1. 行为参数化
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* 2. 使用函数式接口来传递行为
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* 3. 执行一个行为
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* 4. 传递 Lambda
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*/
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public class ExecuteAround {
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private static final String RESOURCE_ROOT = ExecuteAround.class
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.getResource("/").getPath() + "/data-lambda.txt";
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public static void main(String... args) throws IOException {
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// method we want to refactor to make more flexible
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String result = processFileLimited();
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System.out.println(result);
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System.out.println("---");
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String oneLine = processFile(BufferedReader::readLine);
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System.out.println(oneLine);
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String twoLines = processFile((BufferedReader b) -> b.readLine() + b.readLine());
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System.out.println(twoLines);
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}
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public static String processFileLimited() throws IOException {
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try (BufferedReader br =
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new BufferedReader(new FileReader(RESOURCE_ROOT))) {
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return br.readLine();
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}
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}
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public static String processFile(BufferedReaderProcessor p) throws IOException {
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try (BufferedReader br = new BufferedReader(new FileReader(RESOURCE_ROOT))) {
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return p.process(br);
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}
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}
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@FunctionalInterface
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public interface BufferedReaderProcessor {
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String process(BufferedReader b) throws IOException;
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}
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}

‎java8/src/main/java/com/brianway/learning/java8/lambda/FilteringApples.java‎

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/**
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* Created by brian on 16/12/26.
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*
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*
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* 传递代码的例子
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* 分别使用了方法引用和Lambda(匿名函数)
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*/
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public class FilteringApples {
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public static void main(String[] args) {
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}
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/**
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* 根据抽象条件筛选
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* 将迭代集合的逻辑和要应用到集合中每个元素的行为区分开
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* @param inventory
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* @param p
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* @return
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*/
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public static List<Apple> filter(List<Apple> inventory, Predicate<Apple> p) {
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List<Apple> result = new ArrayList<>();
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for (Apple apple : inventory) {

‎java8/src/main/java/com/brianway/learning/java8/lambda/FunctionDescriptor.java‎

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package com.brianway.learning.java8.lambda;
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import java.util.ArrayList;
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import java.util.Arrays;
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import java.util.List;
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import java.util.function.Consumer;
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import java.util.function.Function;
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import java.util.function.Predicate;
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/**
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* Created by brian on 17/2/27.
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* Java 8 中常用函数式接口
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*/
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public class FunctionDescriptor {
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public static void main(String[] args) {
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//使用 Predicate
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Predicate<String> nonEmptyStringPredicate = (String s) -> !s.isEmpty();
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List<String> listOfStrings = Arrays.asList("aaa", "ss", "");
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List<String> nonEmpty = filter(listOfStrings, nonEmptyStringPredicate);
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System.out.println("nonEmpty.size() == 2 " + (nonEmpty.size() == 2));
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//使用 Consumer
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forEach(Arrays.asList(1, 2, 3, 4, 5), System.out::println);
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//使用 Function
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List<Integer> lengthsOfWord = map(
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Arrays.asList("lambda", "in", "action"),
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String::length
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);
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forEach(lengthsOfWord, System.out::println);
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}
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/**
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* 使用 Predicate
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*/
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public static <T> List<T> filter(List<T> list, Predicate<T> p) {
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List<T> results = new ArrayList<>();
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//TODO
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for (T s : list) {
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if (p.test(s)) {
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results.add(s);
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}
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}
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return results;
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}
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/**
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* 使用 Consumer
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*/
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public static <T> void forEach(List<T> list, Consumer<T> c) {
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//TODO
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for (T i : list) {
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c.accept(i);
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}
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}
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/**
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* 使用 Function
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*/
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public static <T, R> List<R> map(List<T> list, Function<T, R> f) {
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List<R> result = new ArrayList<>();
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//TODO
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for (T s : list) {
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result.add(f.apply(s));
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}
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return result;
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}
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}

‎java8/src/main/resources/data-lambda.txt‎

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Java
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8
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Lambdas
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In
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Action

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