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第8章示例代码
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‎src/main/java/com/wbs/java8lambda/chapter8/ChainOfResponsibilityMain.java‎

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package com.wbs.java8lambda.chapter8;
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import java.util.function.Function;
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import java.util.function.UnaryOperator;
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/**
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* TODO
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*
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* @author: wangbingshuai
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* @create: 2019-11-07 11:26
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**/
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public class ChainOfResponsibilityMain {
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public static void main(String[] args) {
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HeaderTextProcessing p1 = new HeaderTextProcessing();
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SpellCheckerProcessing p2 = new SpellCheckerProcessing();
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p1.setSuccessor(p2);
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String result1 = p1.handle("Aren't labdas really sexy?!!");
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System.out.println(result1);
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UnaryOperator<String> headerProcessing = (String text) -> "From Raoul, Mario and Alan: " + text;
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UnaryOperator<String> spellCheckProcessing = (String text) -> text.replaceAll("labda", "lambda");
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Function<String, String> pipeline = headerProcessing.andThen(spellCheckProcessing);
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String result2 = pipeline.apply("Aren't labdas really sexy?!!");
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System.out.println(result2);
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}
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private static abstract class ProcessingObject<T> {
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protected ProcessingObject<T> successor;
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public void setSuccessor(ProcessingObject<T> successor) {
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this.successor = successor;
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}
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public T handle(T input) {
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T r = handleWork(input);
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if (successor != null) {
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return successor.handleWork(r);
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}
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return r;
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}
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abstract protected T handleWork(T input);
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}
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private static class HeaderTextProcessing extends ProcessingObject<String> {
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@Override
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protected String handleWork(String input) {
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return "From Raoul, Mario and Alan: " + input;
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}
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}
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private static class SpellCheckerProcessing extends ProcessingObject<String> {
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@Override
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protected String handleWork(String input) {
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return input.replaceAll("labda", "lambda");
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}
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}
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}

‎src/main/java/com/wbs/java8lambda/chapter8/Debugging.java‎

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package com.wbs.java8lambda.chapter8;
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import java.util.Arrays;
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import java.util.List;
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/**
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* TODO
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*
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* @author: wangbingshuai
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* @create: 2019-11-07 11:58
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**/
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public class Debugging {
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public static void main(String[] args) {
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List<Point> points = Arrays.asList(new Point(12, 2), null);
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points.stream().map(Point::getX).forEach(System.out::println);
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}
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private static class Point {
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private int x;
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private int y;
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public Point(int x, int y) {
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this.x = x;
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this.y = y;
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}
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public int getX() {
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return x;
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}
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public void setX(int x) {
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this.x = x;
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}
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}
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}

‎src/main/java/com/wbs/java8lambda/chapter8/FactoryMain.java‎

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package com.wbs.java8lambda.chapter8;
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import java.util.HashMap;
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import java.util.Map;
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import java.util.function.Supplier;
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/**
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* TODO
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*
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* @author: wangbingshuai
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* @create: 2019-11-06 20:20
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**/
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public class FactoryMain {
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public static void main(String[] args) {
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Product p1 = ProductFactory.createProduct("loan");
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Supplier<Product> loadSupplier = Loan::new;
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Product p2 = loadSupplier.get();
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Product p3 = ProductFactory.createProductLambda("loan");
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}
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private static class ProductFactory {
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public static Product createProduct(String name) {
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switch (name) {
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case "loan":
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return new Loan();
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case "stock":
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return new Stock();
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case "bond":
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return new Bond();
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default:
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throw new RuntimeException("No such product " + name);
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}
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}
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public static Product createProductLambda(String name) {
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Supplier<Product> productSupplier = map.get(name);
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if (productSupplier != null) {
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return productSupplier.get();
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}
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throw new RuntimeException("No such product " + name);
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}
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}
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interface Product {
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}
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private static class Loan implements Product {
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}
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private static class Stock implements Product {
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}
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private static class Bond implements Product {
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}
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final static private Map<String, Supplier<Product>> map = new HashMap<>();
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static {
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map.put("loan", Loan::new);
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map.put("stock", Stock::new);
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map.put("bond", Bond::new);
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}
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}

‎src/main/java/com/wbs/java8lambda/chapter8/ObserverMain.java‎

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package com.wbs.java8lambda.chapter8;
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import java.util.ArrayList;
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import java.util.List;
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/**
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* TODO
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*
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* @author: wangbingshuai
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* @create: 2019-11-06 19:32
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**/
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public class ObserverMain {
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public static void main(String[] args) {
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Feed f = new Feed();
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f.registerObserver(new NYTimes());
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f.registerObserver(new Guardian());
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f.registerObserver(new LeMonde());
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f.notifyObserver("The queen said her favourite book is Java 8 in Action!");
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Feed feedLambda = new Feed();
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feedLambda.registerObserver((String tweet) -> {
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if (tweet != null && tweet.contains("money")) {
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System.out.println("Breaking news in NY! " + tweet);
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}
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});
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feedLambda.registerObserver((String tweet) -> {
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if (tweet != null && tweet.contains("queen")) {
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System.out.println("Yet another news in London... " + tweet);
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}
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});
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feedLambda.notifyObserver("Money money money, give me money!");
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}
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interface Observer {
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void inform(String tweet);
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}
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interface Subject {
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void registerObserver(Observer o);
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void notifyObserver(String tweet);
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}
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private static class NYTimes implements Observer {
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@Override
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public void inform(String tweet) {
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if (tweet != null && tweet.contains("money")) {
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System.out.println("Breaking news in NY!" + tweet);
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}
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}
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}
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private static class Guardian implements Observer {
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@Override
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public void inform(String tweet) {
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if (tweet != null && tweet.contains("queen")) {
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System.out.println("Yet another news in London... " + tweet);
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}
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}
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}
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private static class LeMonde implements Observer {
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@Override
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public void inform(String tweet) {
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if (tweet != null && tweet.contains("wine")) {
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System.out.println("Today cheese, wine and news! " + tweet);
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}
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}
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}
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private static class Feed implements Subject {
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private final List<Observer> observers = new ArrayList<>();
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@Override
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public void registerObserver(Observer o) {
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this.observers.add(o);
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}
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@Override
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public void notifyObserver(String tweet) {
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this.observers.forEach(o -> o.inform(tweet));
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}
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}
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}

‎src/main/java/com/wbs/java8lambda/chapter8/OnlineBanking.java‎

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package com.wbs.java8lambda.chapter8;
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/**
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* TODO
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*
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* @author: wangbingshuai
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* @create: 2019-11-07 11:49
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**/
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abstract class OnlineBanking {
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public void processCustomer(int id) {
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Customer customer = Database.getCustomerWithId(id);
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makeCustomerHappy(customer);
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}
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abstract void makeCustomerHappy(Customer customer);
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private static class Customer {
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}
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private static class Database {
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static Customer getCustomerWithId(int id) {
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return new Customer();
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}
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}
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}

‎src/main/java/com/wbs/java8lambda/chapter8/OnlineBankingLambda.java‎

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package com.wbs.java8lambda.chapter8;
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import java.util.function.Consumer;
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/**
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* TODO
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*
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* @author: wangbingshuai
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* @create: 2019-11-07 11:53
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**/
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public class OnlineBankingLambda {
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public static void main(String[] args) {
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new OnlineBankingLambda().processCustomer(1337, (Customer c) -> System.out.println("Hello!"));
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}
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void processCustomer(int id, Consumer<Customer> makeCustomerHappy) {
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Customer customer = Database.getCustomerWithId(id);
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makeCustomerHappy.accept(customer);
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}
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private static class Customer {
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}
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private static class Database {
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static Customer getCustomerWithId(int id) {
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return new Customer();
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}
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}
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}

‎src/main/java/com/wbs/java8lambda/chapter8/Peek.java‎

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package com.wbs.java8lambda.chapter8;
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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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* TODO
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*
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* @author: wangbingshuai
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* @create: 2019-11-07 15:19
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**/
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public class Peek {
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public static void main(String[] args) {
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List<Integer> result = Stream.of(2, 3, 4, 5)
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.peek(x -> System.out.println("taking from stream:" + x))
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.map(x -> x + 17)
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.peek(x -> System.out.println("after map:" + x))
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.filter(x -> x % 2 == 0)
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.peek(x -> System.out.println("after filter:" + x))
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.limit(3)
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.peek(x -> System.out.println("after limit:" + x))
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.collect(Collectors.toList());
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}
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}

‎src/main/java/com/wbs/java8lambda/chapter8/StrategyMain.java‎

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package com.wbs.java8lambda.chapter8;
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/**
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* TODO
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*
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* @author: wangbingshuai
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* @create: 2019-11-06 19:19
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**/
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public class StrategyMain {
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public static void main(String[] args) {
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// old school
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Validator v1 = new Validator(new IsNumeric());
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System.out.println(v1.validate("aaaa"));
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Validator v2 = new Validator(new IsAllLowerCase());
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System.out.println(v2.validate("bbbb"));
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// with lambdas
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Validator v3 = new Validator((String s) -> s.matches("\\d+"));
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System.out.println(v3.validate("aaaa"));
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Validator v4 = new Validator((String s) -> s.matches("[a-z]+"));
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System.out.println(v4.validate("bbbb"));
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}
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interface ValidationStrategy {
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boolean execute(String s);
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}
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private static class IsAllLowerCase implements ValidationStrategy {
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@Override
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public boolean execute(String s) {
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return s.matches("[a-z]+");
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}
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}
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private static class IsNumeric implements ValidationStrategy {
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@Override
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public boolean execute(String s) {
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return s.matches("\\d+");
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}
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}
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private static class Validator {
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private final ValidationStrategy strategy;
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public Validator(ValidationStrategy strategy) {
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this.strategy = strategy;
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}
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public boolean validate(String s) {
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return strategy.execute(s);
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}
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}
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}

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