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hellokatonhellokaton
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🍱 add lambda examples
1 parent 0719422 commit 4323a7c

6 files changed

Lines changed: 176 additions & 2 deletions

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‎java8-lambda/src/main/java/io/github/biezhi/java8/lambda/lesson2/FunctionalDemo.java‎

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@@ -2,6 +2,7 @@
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import java.util.ArrayList;
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import java.util.List;
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import java.util.UUID;
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import java.util.function.*;
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/**
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*/
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public class FunctionalDemo {
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/**
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* 断言
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*/
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public void predicate() {
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Predicate<String> namesStartingWithS = name -> name.startsWith("s");
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}
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/**
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* 消费数据
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*/
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public void consumer() {
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Consumer<String> messageConsumer = message -> System.out.println(message);
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}
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/**
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* 转换
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*/
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public void function() {
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Function<String, String> toUpperCase = name -> name.toUpperCase();
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}
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/**
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* 提供数据
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*/
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public void supplier() {
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Supplier<String> uuidGenerator = () -> UUID.randomUUID().toString();
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}
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public static void main(String[] args) {
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List<Integer> list = new ArrayList<>();
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Function<String, String> concat = x -> x + 1;
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Integer two = add1.apply(1); //yields 2
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String answer = concat.apply("0 + 1 = "); //yields "0 + 1 = 1"
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String answer = concat.apply("0 + 1 = "); // "0 + 1 = 1"
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BinaryOperator<Integer> sum = (a, b) -> a + b;
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Integer res = sum.apply(1, 2); // yields 3
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Integer res = sum.apply(1, 2); // 3
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BinaryOperator<Function<Integer, Integer>> compose = (f, g) -> x -> g.apply(f.apply(x));
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‎java8-lambda/src/main/java/io/github/biezhi/java8/lambda/lesson3/ConstructorReference.java‎

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package io.github.biezhi.java8.lambda.lesson3;
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import java.util.function.Supplier;
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/**
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* 构造器引用
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* <p>
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* 对于一个现有构造函数， 你可以利用它的名称和关键字 new 来创建它的一个引用： ClassName::new。
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* 它的功能与指向静态方法的引用类似。
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*
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* @author biezhi
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* @date 2018/2/10
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*/
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public class ConstructorReference {
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public static void main(String[] args) {
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//构造器引用
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//根据参数列表自动匹配构造器
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Supplier<ConstructorReference> sup = ConstructorReference::new;
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ConstructorReference constructorReference = sup.get();
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}
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}

‎java8-lambda/src/main/java/io/github/biezhi/java8/lambda/lesson3/DoneByYou.java‎

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package io.github.biezhi.java8.lambda.lesson3;
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import java.util.List;
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import java.util.function.BiPredicate;
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import java.util.function.Function;
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/**
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* 由你完成的
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* <p>
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* 下列Lambda表达式的等效方法引用是什么
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*
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* @author biezhi
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* @date 2018/2/10
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*/
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public class DoneByYou {
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public static void main(String[] args) {
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Function<String, Integer> stringToInteger = (String s) -> Integer.parseInt(s);
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BiPredicate<List<String>, String> contains = (list, element) -> list.contains(element);
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}
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}

‎java8-lambda/src/main/java/io/github/biezhi/java8/lambda/lesson3/LambdaException.java‎

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package io.github.biezhi.java8.lambda.lesson3;
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import java.io.BufferedReader;
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import java.io.IOException;
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import java.util.function.Function;
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/**
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* lambda 中有异常
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* <p>
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* 任何函数式接口都不允许抛出受检异常
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* <p>
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* sf上这个问题的一些讨论：https://stackoverflow.com/questions/18198176/java-8-lambda-function-that-throws-exception
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*
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* @author biezhi
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* @date 2018/2/10
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*/
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public class LambdaException {
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public static void main(String[] args) {
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Function<BufferedReader, String> f = (BufferedReader b) -> {
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try {
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return b.readLine();
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} catch (IOException e) {
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throw new RuntimeException(e);
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}
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};
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}
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}

‎java8-lambda/src/main/java/io/github/biezhi/java8/lambda/lesson3/MethodReference.java‎

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package io.github.biezhi.java8.lambda.lesson3;
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import io.github.biezhi.java8.lambda.lesson1.Project;
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import java.util.Arrays;
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import java.util.List;
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import java.util.function.Predicate;
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import static java.util.stream.Collectors.toList;
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/**
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* 方法引用
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* <p>
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* 1. 指向静态方法的方法引用
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* 2. 指向现有对象的实例方法的方法引用
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*
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* @author biezhi
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* @date 2018/2/10
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*/
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public class MethodReference {
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public static List<Integer> findNumbers(List<Integer> numbers, Predicate<Integer> filter) {
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List<Integer> numbersFound = numbers
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.stream()
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.filter(filter)
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.collect(toList());
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return numbersFound;
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}
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public static boolean multipleOf3(Integer number) {
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return (number % 3) == 0;
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}
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public static void main(String[] args) {
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List<Integer> numbers = Arrays.asList(1, 3, 6, 8, 9, 12, 14, 15);
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List<Integer> multiplesOf3 = findNumbers(numbers, MethodReference::multipleOf3);
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System.out.println(multiplesOf3.contains(3));
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Project project = Project.builder().name("Blade").build();
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Arrays.asList(project).stream()
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.map(Project::getName)
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.count();
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}
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}

‎java8-lambda/src/main/java/io/github/biezhi/java8/lambda/lesson3/OtherReference.java‎

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package io.github.biezhi.java8.lambda.lesson3;
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import java.util.function.Function;
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/**
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* 数组引用
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*
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* @author biezhi
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* @date 2018/2/10
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*/
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public class OtherReference {
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public static void main(String[] args) {
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Function<Integer, String[]> fun = x -> new String[x];
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String[] strs = fun.apply(10);
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System.out.println(strs.length);
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Function<Integer, String[]> fun1 = String[]::new;
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strs = fun1.apply(20);
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System.out.println(strs.length);
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}
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}

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