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Add Stage 1 Lesson 4
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‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
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<project xmlns="http://maven.apache.org/POM/4.0.0"
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xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
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xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
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<parent>
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<artifactId>stage-1</artifactId>
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<groupId>com.segmentfault</groupId>
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<version>1.0-SNAPSHOT</version>
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</parent>
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<modelVersion>4.0.0</modelVersion>
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<artifactId>stage-1-lesson-4</artifactId>
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</project>

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/src/main/java/com/segmentfault/deep/in/java/functional/ActionDemo.java

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package com.segmentfault.deep.in.java.functional;
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public class ActionDemo {
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public static void main(String[] args) {
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// 匿名内置类
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Runnable runnable = new Runnable() {
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@Override
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public void run() {
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System.out.println("小马哥");
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}
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};
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// invokedynamic 指令 @since JDK 1.7
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// 请记住 java.lang.invoke.MethodHandle
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// java.lang.invoke.InvokeDynamic
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Runnable runnable2 = () -> {
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};
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}
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/src/main/java/com/segmentfault/deep/in/java/functional/ConsumerDemo.java

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package com.segmentfault.deep.in.java.functional;
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import java.util.function.Consumer;
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public class ConsumerDemo {
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public static void main(String[] args) {
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Consumer consumer = System.out::println;
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consumer.accept("Hello,World");
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Consumer<String> consumer2 = ConsumerDemo::echo;
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// Fluent API
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// consumer2 -> consumer -> consumer
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consumer2.andThen(consumer).andThen(consumer).accept("Hello,小马哥");
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}
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public static void print(Consumer<? super CharSequence> cs, String message ){
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cs.accept(message);
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}
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private static void echo(String message) {
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System.out.println("echo : " + message);
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}
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/src/main/java/com/segmentfault/deep/in/java/functional/DemoAnnotation.java

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package com.segmentfault.deep.in.java.functional;
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import java.lang.annotation.*;
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@Documented
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@Retention(RetentionPolicy.RUNTIME)
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@Target(ElementType.TYPE)
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public @interface DemoAnnotation {
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String value();
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/src/main/java/com/segmentfault/deep/in/java/functional/DemoAnnotationDemo.java

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package com.segmentfault.deep.in.java.functional;
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@DemoAnnotation(value = "hello")
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public class DemoAnnotationDemo {
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public static void main(String[] args) {
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DemoAnnotation demoAnnotation = DemoAnnotationDemo.class.getAnnotation(DemoAnnotation.class);
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System.out.println(demoAnnotation.value());
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}
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/src/main/java/com/segmentfault/deep/in/java/functional/FunctionDemo.java

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package com.segmentfault.deep.in.java.functional;
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import java.util.function.Function;
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public class FunctionDemo {
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public static void main(String[] args) {
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Function<String, Long> stringToLong = Long::valueOf;
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System.out.println(stringToLong.apply("1"));
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Function<Long, String> longToString = String::valueOf;
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System.out.println(longToString.apply(1L));
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// "1" -> 1L -> "1"
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Long value = stringToLong.compose(String::valueOf).apply(1L);
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}
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/src/main/java/com/segmentfault/deep/in/java/functional/FunctionDesignDemo.java

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package com.segmentfault.deep.in.java.functional;
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import java.util.function.Function;
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public class FunctionDesignDemo {
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public static void main(String[] args) {
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Function function = a -> a;
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// Function 可以用于同类转换
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Function<Integer, Integer> divide2 = a -> a / 2;
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}
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/src/main/java/com/segmentfault/deep/in/java/functional/FunctionalInterfaceDemo.java

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package com.segmentfault.deep.in.java.functional;
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public class FunctionalInterfaceDemo {
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public static void main(String[] arg) {
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Function1 function1 = () -> {
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};
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FunctionalInterfaceWithoutAnnotation f2 = () -> {
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};
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}
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@FunctionalInterface
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public interface Function1 {
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public abstract void execute();
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// 不能出现两次抽象方法定义
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// void execute2();
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default String getDescription() {
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return String.valueOf(this);
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}
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}
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// @FunctionalInterface // @FunctionalInterface 并非必选的
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public interface FunctionalInterfaceWithoutAnnotation {
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void execute();
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}
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// @FunctionalInterface // @FunctionalInterface 只能描述接口
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// public class FunctionClass {
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//
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// }
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/src/main/java/com/segmentfault/deep/in/java/functional/PredicateDemo.java

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package com.segmentfault.deep.in.java.functional;
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import java.io.File;
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import java.io.FileFilter;
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import java.util.function.Predicate;
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public class PredicateDemo {
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public static void main(String[] args) {
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Predicate<File> predicate = file -> true;
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}
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}

‎「一入 Java 深似海 」/代码/segmentfault/deep-in-java/stage-1/lesson-4/src/main/java/com/segmentfault/deep/in/java/functional/PredicateDesignDemo.java

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package com.segmentfault.deep.in.java.functional;
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import java.util.*;
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import java.util.function.Predicate;
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import java.util.stream.Stream;
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public class PredicateDesignDemo {
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public static void main(String[] args) {
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List<Integer> numbers = Arrays.asList(1, 2, 3, 4, 5);
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Collection<Integer> even = filter(numbers, num -> num % 2 == 0);
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Collection<Integer> odd = filter(numbers, num -> num % 2 != 0);
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System.out.println(odd);
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System.out.println(even);
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Stream.of(1, 2, 3, 4, 5).filter(num -> num % 2 == 0).forEachOrdered(System.out::println);
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}
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private static <E> Collection<E> filter(Collection<E> source, Predicate<E> predicate) {
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// 集合类操作，请不要直接利用参数
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List<E> copy = new ArrayList<E>(source);
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Iterator<E> iterator = copy.iterator();
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while (iterator.hasNext()) {
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E element = iterator.next();
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if (!predicate.test(element)) {
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iterator.remove();
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}
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}
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return Collections.unmodifiableList(copy);
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}
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}

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