南通网站建设培训,婚恋网站开发背景文献,网站百度百科,中国十大电商平台排行榜java8 streams我一直落后于Java 8所关注的功能#xff0c;因此在这篇文章中#xff0c;我将简要介绍我对lambda和stream的初步经验。 和往常一样#xff0c;我将专注于Podcast课程#xff1a; package org.codingpedia.learning.java.core;import java.util.Comparator;p… java8 streams 我一直落后于Java 8所关注的功能因此在这篇文章中我将简要介绍我对lambda和stream的初步经验。 和往常一样我将专注于Podcast课程 package org.codingpedia.learning.java.core;import java.util.Comparator;public class Podcast {int id;String title;String producer;int subscriptionsNumber;/** number of up votes(likes) */int upVotes;/** number of down votes*/int downVotes;public Podcast() {this.subscriptionsNumber 0;}public Podcast(int id, String title, String producer, int subscriptionsNumber, int upVotes, int downVotes) {this.id id;this.title title;this.producer producer;this.subscriptionsNumber subscriptionsNumber;this.upVotes upVotes;this.downVotes downVotes;}public static final ComparatorPodcast BY_POSITIVE_VOTES_DIFFERENCE (left, right) - (right.getUpVotes()-right.getDownVotes()) - (left.getUpVotes()-left.getDownVotes());Overridepublic String toString() {return Podcast{ title title \ , producer producer \ , upVotes upVotes , downVotes downVotes , subscriptionsNumber subscriptionsNumber };}public static String toJSON(Podcast p) {return { title: p.title \ , producer: p.producer \ , upVotes: p.upVotes , downVotes: p.downVotes , subscriptionsNumber: p.subscriptionsNumber };}public int getUpVotes() {return upVotes;}public void setUpVotes(int upVotes) {this.upVotes upVotes;}public int getDownVotes() {return downVotes;}public void setDownVotes(int downVotes) {this.downVotes downVotes;}public String getTitle() {return title;}public void setTitle(String title) {this.title title;}public String getProducer() {return producer;}public void setProducer(String producer) {this.producer producer;}public int getSubscriptionsNumber() {return subscriptionsNumber;}public void setSubscriptionsNumber(int subscriptionsNumber) {this.subscriptionsNumber subscriptionsNumber;}public int getId() {return id;}public void setId(int id) {this.id id;}
} 我将在用lambda和流构建的不同操作中使用它。 但是这次我将让代码说明一切 Lambda和流示例 package org.codingpedia.learning.java.core;import java.util.*;
import java.util.function.Predicate;
import java.util.stream.Collectors;public class LambdasAndStreams {public static void main(String[] args) {ListPodcast podcasts Arrays.asList(//new Podcast(podcastId, title, producer, subscriptionsNumber, upVotes, downVotes),new Podcast(1, QuarksCo, wdr, 50, 18, 1),new Podcast(2, Angeklickt - zum Mitnehmen, wdr, 10, 5, 1),new Podcast(3, Leonardo im WDR 5-Radio zum Mitnehmen, wdr, 12, 10, 5),new Podcast(4, LESPRIT PUBLIC, France culture, 3, 10, 1),new Podcast(5, LA FABRIQUE DE LHISTOIRE, France culture, 10, 4, 1),new Podcast(6, LES MATINS DE FRANCE CULTURE, France culture, 46, 12, 8));System.out.println(*********** Display initial podcasts with forEach ************);podcasts.forEach(podcast - System.out.println(podcast));System.out.println(\n\n********************** Sorting with lambdas ***********************);// Sort by titleSystem.out.println(\n*********** Sort by title (default alphabetically) - highlight comparator ************);Collections.sort(podcasts, Comparator.comparing(Podcast::getTitle));podcasts.forEach(podcast - System.out.println(podcast));System.out.println(\n*********** Sort by numbers of subscribers DESCENDING - highlight reversed ************);Collections.sort(podcasts, Comparator.comparing(Podcast::getSubscriptionsNumber).reversed());podcasts.forEach(podcast - System.out.println(podcast));System.out.println(\n*********** Sort by producer and then by title - highlight composed conditions************);Collections.sort(podcasts, Comparator.comparing(Podcast::getProducer).thenComparing(Podcast::getTitle));podcasts.forEach(podcast - System.out.println(podcast));System.out.println(\n*********** Sort by difference in positive votes DESCENDING ************);Collections.sort(podcasts, Podcast.BY_POSITIVE_VOTES_DIFFERENCE);podcasts.forEach(podcast - System.out.println(podcast));System.out.println(\n\n******************** Streams *************************);System.out.println(\n*********** Filter podcasts with more than 21 subscribers - highlight filters ************);podcasts.stream().filter((podcast)- podcast.getSubscriptionsNumber() 21).forEach((podcast)-System.out.println(podcast));System.out.println(\n********* Filter podcasts from producer with more than 21 subscribers - highlight predicate **************);PredicatePodcast hasManySubscribers (podcast) - podcast.getSubscriptionsNumber() 21;PredicatePodcast wdrProducer (podcast) - podcast.getProducer().equals(wdr);podcasts.stream().filter(hasManySubscribers.and(wdrProducer)).forEach((podcast) -System.out.println(podcast));System.out.println(\n********* Display popular podcasts - highlight \or\ in predicate **************);PredicatePodcast hasManyLikes (podcast) - (podcast.getUpVotes()-podcast.getDownVotes()) 8;podcasts.stream().filter(hasManySubscribers.or(hasManyLikes)).forEach((podcast) -System.out.println(podcast));System.out.println(\n********* Collect subscription numbers - highlight \mapToInt\ **************);int numberOfSubscriptions podcasts.stream().mapToInt(Podcast::getSubscriptionsNumber).sum();System.out.println(Number of all subscriptions : numberOfSubscriptions);System.out.println(\n********* Display podcast with most subscriptions -highlight \map reduce\ capabilities **************);Podcast podcastWithMostSubscriptions;podcastWithMostSubscriptions podcasts.stream().map(podcast - new Podcast(podcast.getId(), podcast.getTitle(), podcast.getProducer(), podcast.getSubscriptionsNumber(), podcast.getUpVotes(), podcast.getDownVotes())).reduce(new Podcast(),(pod1, pod2) - (pod1.getSubscriptionsNumber() pod2.getSubscriptionsNumber()) ? pod1 : pod2);System.out.println(podcastWithMostSubscriptions);System.out.println(\n********* Display podcasts titles in XML format -highlight \map reduce\ capabilities **************);String titlesInXml podcasts datatitles podcasts.stream().map(podcast - title podcast.getTitle() /title).reduce(, String::concat) /podcasts;System.out.println(titlesInXml);System.out.println(\n********* Display podcasts in JSON format -highlight \map reduce\ capabilities **************);String json podcasts.stream().map(Podcast::toJSON).reduce([, (l, r) - l (l.equals([) ? : ,) r) ];System.out.println(json);System.out.println(\n********* Display sorted podcasts by title in JSON format -highlight \map collect\ capabilities **************);String jsonViaCollectors podcasts.stream().sorted(Comparator.comparing(Podcast::getTitle)).map(Podcast::toJSON).collect(Collectors.joining(,, [, ]));System.out.println(jsonViaCollectors);System.out.println(\n********* Select first 3 podcasts with most subscribers -highlight \map collect\ capabilities **************);ListPodcast podcastsWithMostSubscribers podcasts.stream().sorted(Comparator.comparing(Podcast::getSubscriptionsNumber).reversed()).limit(3).collect(Collectors.toList());System.out.println(podcastsWithMostSubscribers);System.out.println(\n********* Get podcasts grouped by producer -highlight \collector\ capabilities **************);MapString, ListPodcast podcastsByProducer podcasts.stream().collect(Collectors.groupingBy(podcast - podcast.getProducer()));System.out.println(podcastsByProducer);}
}资源资源 Java 8中央 Java 8Lambda第1部分 Java 8Lambdas第2部分 翻译自: https://www.javacodegeeks.com/2015/03/yet-another-java-8-lamdbas-and-streams-example.htmljava8 streams
