java-ee - java8的Collectors.reducing(）

{Code...} Probably I want to group the operationInfos collection according to the cityId in it, and then if the cityId is the same, add the SurgeryCount of the object and return it, but now the first v1 is null, execute v1.setSurgeryCount(v1. getSurgeryCount() + v2.g...

三叔 2017-07-03 11:43:35 0 1 1015

lambda - java8 An object is arranged in the order of a certain field in the object

For example, I want to have a class User with attributes like this: private int age, private String name, several objects {code...} Now I want to sort them in ascending order of age, that is, the final display result of lisr is user1 user3 user2. How to write it using lambda expression in java8? thi...

欧阳克 2017-06-23 09:13:33 0 3 749

Are there any concurrency issues when using Java8's stream to operate external collections?

Description: Take out the non-DataTime in cp. Is the following code reasonable? Is there any concurrency problem with deviceDataMap? Map<String,Map<String,String>> deviceDataMap = new HashMap<>(); String cp = "DataTime=200405060101.

代言 2017-06-23 09:13:05 0 1 657

How to get the time of last month through LocalDate in java8

As the title says, LocalDate has many methods about next, so how can I get the time of last month through Localdate? It can also be a certain day of last month. Then I can intercept the string, and finally it will be like "2017-06"

大家讲道理 2017-06-14 10:52:53 0 2 753

java-ee - JAVA8 lambdas expression changes the value of external variables

As shown in the picture, I defined an etotalPrice externally, and then tried to change this value in two for loops, but an error was reported to me. How to solve it? (NumberUtil.add and mutiplyu are the basic +*methods of retaining 2 decimal places)

天蓬老师 2017-06-12 09:24:10 0 3 667

About lambda expressions, static method references and stream api iteration in the new features of java8

I am new to the syntax of Java 8 and already have a preliminary understanding of the use of lambda expressions alone, the static method reference notation of 1.8 and the reference of forEach() in the stream API of 1.8. However, during the exercise, I encountered the following code: { Code...} For th...

世界只因有你 2017-05-17 10:04:45 0 2 535

In java8, what does the logical and & symbol mean when used on interface classes?

Recently I was reading the java source code related to lambda expressions, and found a lot of similar writing methods in the static methods of Comparator {code...} Among them, return (Comparator<T> & Serializable) should mean forced type conversion, but here Why not just convert to...

ringa_lee 2017-05-17 09:58:41 0 1 532

java - Spring MVC无法识别Controller导致返回的结果是404？

运行环境 java8 + idea2016 + spring mvc4.3 + maven3.3 + tomcat8 + ubuntu 报错信息 访问localhost:8080/HelloWeb/hello或者localhost:8080/hello都会返回404的状态码： 具体配置 项目结构 Web.xml {代码...} H...

阿神 2017-04-18 10:55:44 0 6 358

java - Eclipse：为何方法默认未显示注释，鼠标悬浮却可以看到注释呢？

查看Java8中CompletableFuture.java的源码，发现thenApply方法上面没有写注释，但是将鼠标放到thenApply上面却可以看到注释，请问这是为什么呢?

迷茫 2017-04-18 10:49:49 0 3 400

Java8Stream异常处理

我也是刚用上Java8的Stream，所有的一切都还在照猫画虎的阶段。 在异常处理这块不敢贸然前进，因为我看到某篇文的这样一段话 在单线程环境中，使用捕获受检异常并重新抛出非受检异常的方法是可行的。但是在多线程...

PHPz 2017-04-18 10:48:40 0 2 566

java8 - java.nio.charset.MalformedInputException: Input length = 2

{代码...} {代码...} 百度之后的结果都是对java NIO Exception in thread "main" java.nio.charset.MalformedInputException: Input length = 1这种的回答。我的文件是utf-8编码的，文件很大，所以就没有上传了。...

大家讲道理 2017-04-18 10:45:13 0 2 1266

java8 stream groupby后的数据结构是否可以重构

{代码...} 这样分组后，得到的数据结构，key是分组的组名，我想要的是可以重构这个分组后的数据结构，用myKey：key，myValue:当前组对应的分组的数据 应该怎么一句话写完？因为我现在没办法，只能再写一个循环，...

ringa_lee 2017-04-18 10:17:57 0 1 725

java - myeclipse2015使用的疑问

刚换到myeclipse2015版，各种不适应，之前用的是10版，主要不支持java8，才换到2015版的。 一个小问题：我这边content assit快捷键设置的是alt+j，然后在jsp，xml中写使用这个代码补全时就会出现问题，如下： 比...

迷茫 2017-04-18 10:16:11 0 0 285

java - Selenium调用IE出错SessionNotCreatedException

从头到尾看了几遍官方文档，也把IEDriverServer.exe加入了PATH，也试过 {代码...} 这样加载，代码就一句： {代码...} 但是报错 {代码...} 试了很多windows版本和IE版本，selenium3.0和3.0.1都试了，java8环境64位...

阿神 2017-04-18 10:12:21 0 3 267

java8 怎么一次遍历两个list

常规方法如下，伪代码， 有更优雅的方法吗 java8都可以。 {代码...}

高洛峰 2017-04-18 10:09:07 0 2 250

java8 flatmap

java8 stream 的 flatmap 跟map有啥区别？有例子不

天蓬老师 2017-04-18 09:59:19 0 3 250

用Java8的forEach遍历问题

用Java8 forEach遍历，代码如下： 抛出这样的一个错误： 即便是将局部变量设为final一样报错？搞不明白啦

天蓬老师 2017-04-18 09:56:15 0 4 280

大家平时用Java8吗？用了哪些新的特性吗？

我看到有报告说现在Java 8用的比较多，比JDK 7要多。大家平时用Java 8吗?是像Java 7一样的用?还是用了哪些新的特性吗？

迷茫 2017-04-18 09:55:21 0 3 338

java8 Stream函数式

rt,比如有个ArrayList a，泛型为B，我想去判断如果B中某个字段（假如getFieldX）不为null,执行一种操作，为null执行另一种，请问框架怎么写?要函数式那种

迷茫 2017-04-18 09:35:35 0 2 272

java框架选型 Guava vs Lambdaj

需求 查询用户最近的中奖信息 并返回中奖名单列表 纯Java7实现 {代码...} 评价 感觉非常繁琐 特别是当你习惯了Java8的函数式编程后 Guava实现 {代码...} 评价 代码不够简洁， 看的时候还是容易被这些匿名内部类干...

天蓬老师 2017-04-18 09:19:00 0 3 351