programming in scala

Mappings and tuples Summary :A classic programmer's famous saying is: "If there is only one data structure, then use a hash table." A hash table , or more generally, a mapping , is one of the most flexible data structures. A map is a collection of key/value duality . Scala has a common term: tuples, which are aggregates of N objects, do not necessarily have the same type . duality is simply a n=2 tuple, and tuples are especially useful for

Tag: Spark installs Scala1. Download SparkHttp://mirrors.cnnic.cn/apache/spark/spark-1.3.0/spark-1.3.0-bin-hadoop2.3.tgz2. Download ScalaHttp://www.scala-lang.org/download/2.10.5.html3. Install ScalaMkdir/usr/lib/scalaTAR–ZXVF scala-2.10.5.tgzMV Scala-2.10.5/usr/lib/scala4. Set Scala pathVim/etc/bashrcExport scala_home=/usr/lib/

Scala supports associative mappings, such as a key-value pair that can be represented by (key, value) All types in Scala are objects, including basic data types The case statement in Scala is used to determine the received message, which is more than the switch...case in Java ... More focusedreceive{Case msg = action ()} The

In the previous chapter we introduced and then used the interpreter to write simple Scala code, and here's how to write a Hello word! using eclipse Open Eclipse. Create a new Scala Project. The first new words should be in other, name casually, then create a new Scala Object named "HelloWorld". Unlike Scala and Java, t

To this chapter, the examples of all function texts refer only to the arguments passed in. For example, (x:int) => x > 0, the only variable used by the function body, x > 0, is x, which is defined as a function argument. However, you can also refer to variables defined elsewhere: (x:int) => x + much/more. 51CTO Editorial Recommendations: A special topic in Scala programming languages function to add "more" to the reference, but what is more it. From

=${java_home}/bin:$PATH 5 Execute java-version and javac-version if it can appear the instructions shown in Java installation complete　　Step Two: Install the Scala https://scala-lang.org/download/page to download1, wget https://downloads.lightbend.com/scala/2.12.6/scala-2.12.6.tgz2, unzip TAR-ZXF

* @param spark*/ Private Static voidDynamictransform (Sparksession Spark) {Javardd"StuInfo.txt"). Javardd (); Javardd{string[] parts= Line.split (","); String Sid= parts[0]; String sname= parts[1]; intSage = Integer.parseint (parts[2]); returnrowfactory.create (SID, Sname, Sage ); }); ArrayListNewArraylist(); Structfield Field=NULL; Field= Datatypes.createstructfield ("Sid", Datatypes.stringtype,true); Fields.Add (field); Field= Datatypes.createstructfi

Brief introductionThere are no enumeration types in Scala, but the enumeration class is provided in the standard class library to produce enumerations. After extending the enumeration class, call the value method class to initialize the possible values in the enumeration.The inner class value is actually an abstract class, and the real creation is Val. Because it is actually Val, you can pass in the ID and name for value. If not specified, the ID is a

Scala Arrays and lists:Import Scala.collection.mutable.ArrayBufferimport scala.collection.mutable.Bufferobject arraylearning {def main ( Args:array[string]): Unit = {//usezipunzip//listops//arrayops//arraybufferops} private def Usezipunzip = {//zip and unzip Val nums = List (1, 2, 3, 4) Val chars = List (' A ', ' B ', ' C ', ' d ') val combinlist = Nums.zi P (chars) println (combinlist) println (Combinlist.unzip)} private def arraybufferops = {//crea

The Withprintwriter method shown in the previous section differs from the built-in control structure of the language, such as if and while, where the code with the braces is parameterized. The Withprintwriter method requires a parameter of type PrintWriter. This parameter is displayed in the "writer =>" way: Withprintwriter (file) { writer => writer.println (new java.util.Date) } However, if you want to implement something more like if or while, there is no value to pass the code between the

At the time of writing, the summer is coming to an end, the new school year is about to begin, and Twitter's servers are constantly popping up with updates released by the world's web bugs and non-web bugs. For many of us in North America, from beach parties to football, from outdoor entertainment to indoor projects, all sorts of ideas are pouring in. To keep up with the situation, it is time to revisit Scitter, the Scala client library that is used t

Label:Read Oracle data in Scala After adding the Oralce jar package Package cn.bigdata.scala.oracle Import java.sql.{ DriverManager, Connection, ResultSet} object Connectoracle { val user= "Youname" val password = "Youpwd" val conn_str = "Jdbc:oracle:thin: @ip: 1521:database"; println (CONN_STR) def main (args:array[string]): Unit ={ //classof[com.mysql.jdbc.driver] Class.forName ("Oracle.jdbc.OracleDriver")//.newinstance

I. Fixed-length arraysIf you need an array of the same length, you can use the array in Scala. Val nums = new Array[int] (10)val s = Array ("Hello", "World")Two. Variable-length array: array buffering 1. val b = Arraybuffer[int] () 2. Append elements B + = (1,2,3,4,5) 3. Append any set b ++= Array (8,13,21) 4. Removal of the last 5 elements b.trimend (5) 5. Inserting elements B.insert (2,6) 6. Insert any number of elements

Package Com.xing.listfile/** * Created by Dengni on 2017/2/12. * Scala type System programming Combat: * 1,scala classes and methods, functions can be generic, in the spark source code can be seen everywhere the generics of classes and methods, in the actual instantiation of the type of specific *, such as spark the most core, most basic, most important abstract data structure Rdd the definition of the Rdd

The array inside the 1.scala is similar to that in Java, but there are some different ways of initializing the array, which is a bit more than Java, as follows: The code is as follows: Package Com.scala.demo /** * Here is the main introduction to the use of the array /object ArrayDemo2 { val array=new Array[int] (3) Val array2=new Array[int] (3) Val array3=new Array[int] (3) /** * Array Assignment operation 1 /def init1 () { Array

1. Initializing an array To initialize an array, you can use the New keyword, as in Java, to specify the data type and the array length. def test () = { val arr = new Array[int] (3) arr.foreach (x = print (x + ",")) } After the above code is run up: 0,0,0, You can also provide the initial value directly without using the New keyword: def test () = { val arr = Array[int] (3) arr.foreach (x = print (x + ",")) } Note that when the run is up, the r

Java will be a platform rather than a programming language. The original engineers of Java made a wise decision to separate the programming language from the runtime environment, which eventually allowed over 200 languages to run on the Java platform. This architecture is crucial to the long-term vitality of the platform, because the computer programming language generally has a short life cycle. The annual JVM language summit, sponsored by Oracle, started in 2008, provided an opportunity for op

Scala learning document directory 1. Array 2. List 3. Map 4. Break 5. If else 6. 7. foreach 8. Option 9. tuple 10. Code conventions 11. Request to accept array or array content 12. Array usage 1) Scala Definition General Definition: Val array1 = array [String] ("str1", "str2 ") Array of specific length: Val array2 = new array [list [int] (Leng) 2) The array cannot be extended. Therefore, you can define arra

First, REPLThe Scala interpreter reads an expression, evaluates it, prints it out, and then continues to read the next expression. This process is called a read-print-loop, or REPL.Technically speaking, the Scala program is not an interpreter. What actually happens is that the content you enter is quickly compiled into bytecode, which is then handed to the Java Virtual machine for execution. Because of this

This is a creation in Article, where the information may have evolved or changed. Format conversion Classes category Python Java Scala Go Excel XLWT/XLRD, Xlsxwriter Poi - - Pdf PyPDF2 Apache FOP - - Csv Csvkit, Tablib - - - XML parsing Beautifulsoup/bs4 - - - Json - Jackson Json4s, Spr