java 8 flatmap

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Reactor Introduction and Practice

This is a creation in Article, where the information may have evolved or changed. Suitable for reading: This article is suitable for the spring, Netty and other frameworks, as well as the Java 8 Lambda, Stream and other features have a basic understanding of the spring 5 to understand the reactive programming characteristics of technical staff reading. First, preface In recent years, with the advent of new

Java Functional Programming (12): Monitoring file Modification _java

-it combines two consecutive operations together, often called tuples-with an elegant operation. We already know how to use the Flatmap () method to list all the files in a direct subdirectory. Now let's monitor the file modification operation. Monitoring file Modification We already know how to find files and directories, but this is also very simple if we want to be able to receive prompt messages when files are created, modified, or deleted. Suc

Java 8 Optional class depth parsing

Original link: Javacodegeeks translation: importnew.com-Go JunyangLink: http://www.importnew.com/6675.htmlAs a Java programmer, you might have the experience of calling a method to get a return value but not invoking the return value directly as a parameter. We will first determine if the return value is null and can be used as a parameter to other methods only if it is not null. This is what some of the external APIs like Guava are trying to solve. S

In Java, if NULL and NULL are encountered, use optional to resolve the situation.

If null and empty are encountered in Java, use optional to resolveExample code:1 PackageCrazy;2 3 Importjava.util.Optional;4 5 classCompany {6 PrivateString name;7 PrivateOptionalOffice;8 9 PublicCompany (String name, optionalOffice) {Ten This. Name =name; One This. Office =Office; A } - - PublicString GetName () { the returnname; - } - - PublicOpt

JAVA8 Map Flatmap

Map: For the elements contained in the stream, the newly generated stream contains only the elements that are generated by the transformation, using the given conversion function. This method has three variant methods for the original type, namely Maptoint,maptolong and maptodouble. These three methods are also better understood, for example Maptoint is to convert the original stream into a new stream, and the elements in the newly generated stream are of type int. There are three variants that

How to Avoid NULL pointer exceptions using Java 8 Optional

= computer.flatMap(Computer::getSoundcard) .flatMap(Soundcard::getUSB) .map(USB::getVersion) .orElse("UNKNOWN"); The first flatMap ensures that the returnedOptionalInsteadOptional, The second flatMap implements the same function and returnsOptional. Note that the third callmap()BecausegetVersion()Returns a String object instead of an Optional object.

Turn: Easy to Rxjava (ii: operator)

change the flow of data. Once we want to change each URL, we can only do it in subscriber. We did not use such a cool map () operator!!!Of course, I can use the map operator, map input is the list of URLs, processing time or for each traversal, just as the egg hurts.Fortunately, there is also the Observable.from () method, which receives a collection as input, and then outputs one element at a time to the Subscriber:[Java]View PlainCopy Obse

Java 8 (9) optional replace null

) { return Person.flatmap (P--Car.map (C-- getinsurance (P, c)); }If P is empty, the returned empty optional object is not executed. If the car is empty, it will not perform a return empty optional object. Call this method if all have values.Filter to reject specific valuesIn addition to the operations in the map and Flatmap methods like streams, there is a filter method. Use filter to quickly determine whether the optional object contains

The SWIFT essential function map you need to know

array of each element? 10 and then converted to a string; I hope you understand the closure of the package first;Flatmap functionWhen it comes to map functions, it's natural to talk about Flatmap,flatmap and map functions, but there are other differences.Map can do a map operation on all elements of a collection type. What about

Improve the performance of spark by partitioning (partitioning)

for more information.Spark context available as sc.SQL context available as sqlContext.scala> val n = 2000000n: Int = 2000000scala> val composite = sc.parallelize(2 to n, 8).map(x => (x, (2 to (n / x)))).flatMap(kv => kv._2.map(_ * kv._1))composite: org.apache.spark.rdd.RDD[Int] = MapPartitionsRDD[2] at flatMap at :29scala> scala> val prime = sc.parallelize(2 to

"Original Hadoop&spark Hands-on 5" Spark Basics Starter, cluster build and Spark Shell

Introduction to spark Basics, cluster build and Spark ShellThe main use of spark-based PPT, coupled with practical hands-on to enhance the concept of understanding and practice.Spark Installation DeploymentThe theory is almost there, and then the actual hands-on experiment:Exercise 1 using Spark Shell (native mode) to complete wordcountSpark-shell to Spark-shell native modeFirst step: Import data by file modescala> val rdd1 = Sc.textfile ("File:///tmp/wordcount.txt")Rdd1:org.apache.spark.rdd.rdd

Example of using Spark operators

Javasparkcontext (conf); list 2.2.3 Scala Sample def filter { val conf = new sparkconf (). Setappname (ScalaOperatorDemo.getClass.getSimpleName). Setmaster ("local") val sc = new Sparkcontext (conf) val datas = Array (1, 2, 3, 7, 4, 5, 8) sc.parallelize (datas) . Filter (v = Gt V >= 3) . foreach (println) } 2.3 FlatMap 2.3.1 Brief Introduction Syntax (Scala): def

Functional Programming (30)-Functional Io:free Monad-monad production line

(fa,g) = bind (FA, G andthen (_ FlatMap F))9 }Tendef map[b] (f:a = B): free[f,b] = flatMap (A =Return (f (a))) One A } - Case classReturn[f[_],a] (A:A)extendsFree[f,a] - Case classBind[f[_],i,a] (a:f[i], f:i = Free[f,a])extendsFree[f,a]we can use the following lift function to upgrade interact[a] to Free[f,a] :1 Implicit def Lift[f[_],a] (Fa:f[a]): free[f,a] = Bind (FA, (a:a) = Return (A))2

With 2:reactor 3 selection of the appropriate operator--response spring's DAO spell device

by means of a method). 8) Back to the synchronized world I have one Flux , I think: Block before getting the first element:Flux#blockFirst ... And give the time-out period:Flux#blockFirst(Duration) Blocks before getting the last element (returns NULL if the sequence is empty):Flux#blockLast ... And give the time-out period:Flux#blockLast(Duration) To convert synchronously to Iterable :Flux#toIterable

Java8 Learning (1)-Lambda experience Zone

Oracle began formally introducing lambda expressions in Java8, although it was a bit late, but as a Java developer we were excited. Before we get into formal learning, we now experience the magic of lambda.We quote a wonderful translation from Importnew: Java8: Don't use loops as an experiential project.In this article, we will look at some of the alternatives to traditional loops. In the new features of Java

Upgrading to Java 8--Chapter III Optional and Similar Classes

method receives a consumer function interface that is called if the value exists, so if you want to print the value simply, you can:optional.ifPresent(System.out::println);If the value exists, nothing will happen.The Flatmapfang method applies a mapping method and returns a value that is described by a optional, more than that, which can be called by cascading, as follows to check for a series of NULL cases:Company1.flatmap (company::getoffice).

JAVA 8 Optional class introduction and its source code, javaoptional

JAVA 8 Optional class introduction and its source code, javaoptionalWhat is an Optional object? The so-called Optional object in Java 8 is a container object, which can contain a null or non-null value. If the value is not null, true is returned when the isPresent () method is called, and the get () method is called. I

Java basic operation of the stream for list

Reference Blog: HTTPS://WWW.JIANSHU.COM/P/9FE8632D0BC2About Stream Java 8 introduces a new stream API. This stream differs from the I/O stream in that it is more like a collection class with iterable, but behaves differently from the collection class. Stream is an enhancement to the functionality of a collection object, focusing on a variety of very convenient, efficient aggregation operations

Simplifying code with Kotlin

since Google in the IO conference to designate Kotlin as the first level of Android language, Kotlin's popularity is brush brushes up, so, let us look at Kotlin what is the advantage, Google why to use it as the first language of Android? 1.100% compatible Java This is the most important point, because Kotlin is also running on the JVM, and even compiled bytecode files are the same, even directly with the JDK, directly using the

Rxjava memory leak resolution in Android and Rxjava package

); }@Override Public void _OnError(String msg) { } });Without adding. Compose (rxlifecycle.binduntilevent (Lifecycle (), activityevent.stop), click the button to upload and immediately return to the log log of the previous activity:After returning to Mainactivity, about 2 seconds later, this sentence appears.05-0618:37:58.59015642-15642/com.sanniuben.myapplication E/way: aaaaAfter the addition, there was no return.It can be seen that he cance

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