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translating scala
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Pablo Arranz Ropero
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es-es/scala.html.markdown
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es-es/scala.html.markdown
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---
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language: Scala
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filename: learnscala-es.scala
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contributors:
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- ["George Petrov", "http://github.com/petrovg"]
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- ["Dominic Bou-Samra", "http://dbousamra.github.com"]
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- ["Geoff Liu", "http://geoffliu.me"]
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- ["Ha-Duong Nguyen", "http://reference-error.org"]
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translators:
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- ["Pablo Arranz Ropero", "http://arranzropablo.com"]
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lang: es-es
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---
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Scala - El lenguaje escalable
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```scala
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/////////////////////////////////////////////////
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// 0. Básicos
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/////////////////////////////////////////////////
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/*
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Configurar Scala:
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1) Descarga Scala - http://www.scala-lang.org/downloads
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2) Unzip/untar a tu carpeta elegida y pon la subcarpeta bin en tu variable de entorno `PATH`
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*/
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/*
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Prueba REPL
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Scala tiene una herramienta llamada REPL (Read-Eval-Print Loop, en español: Bucle de lectura-evaluación-impresión) que es analogo a interpretes de la linea de comandos en muchos otros lenguajes.
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Puedes escribir cualquier expresión en Scala y el resultado será evaluado e impreso.
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REPL es una herramienta muy práctica para testear y verificar código.
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Puedes usarla mientras lees este tutorial para explorar conceptos por tu cuenta.
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*/
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// Inicia Scala REPL ejecutando `scala` en tu terminal. Deberías ver:
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$ scala
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scala>
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// Por defecto cada expresión que escribes es guardada como un nuevo valor numerado:
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scala> 2 + 2
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res0: Int = 4
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// Los valores por defecto pueden ser reusados. Fíjate en el tipo del valor mostrado en el resultado...
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scala> res0 + 2
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res1: Int = 6
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// Scala es un lenguaje fuertemente tipado. Puedes usar REPL para comprobar el tipo sin evaluar una expresión.
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scala> :type (true, 2.0)
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(Boolean, Double)
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// Las sesiones REPL pueden ser guardadas
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scala> :save /sites/repl-test.scala
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// Se pueden cargar archivos en REPL
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scala> :load /sites/repl-test.scala
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Loading /sites/repl-test.scala...
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res2: Int = 4
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res3: Int = 6
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// Puedes buscar en tu historial reciente
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scala> :h?
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1 2 + 2
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2 res0 + 2
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3 :save /sites/repl-test.scala
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4 :load /sites/repl-test.scala
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5 :h?
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// Ahora que sabes como jugar, aprendamos un poco de Scala...
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/////////////////////////////////////////////////
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// 1. Básicos
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/////////////////////////////////////////////////
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// Los comentarios de una linea comienzan con dos barras inclinadas
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/*
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Los comentarios de varias lineas, como ya has visto arriba, se hacen de esta manera.
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*/
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// Así imprimimos forzando una nueva linea en la siguiente impresión
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println("Hola mundo!")
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println(10)
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// Hola mundo!
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// 10
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// Así imprimimos sin forzar una nueva linea en la siguiente impresión
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print("Hola mundo")
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print(10)
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// Hola mundo10
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// Para declarar valores usamos var o val.
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// Valores decalrados con val son inmutables, mientras que los declarados con var son mutables.
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// La inmutabilidad es algo bueno.
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val x = 10 // x es 10
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x = 20 // error: reassignment to val
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var y = 10
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y = 20 // y es 20
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/*
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Scala is a statically typed language, yet note that in the above declarations,
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we did not specify a type. This is due to a language feature called type
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inference. In most cases, Scala compiler can guess what the type of a variable
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is, so you don't have to type it every time. We can explicitly declare the
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type of a variable like so:
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*/
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val z: Int = 10
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val a: Double = 1.0
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// Notice automatic conversion from Int to Double, result is 10.0, not 10
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val b: Double = 10
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// Boolean values
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true
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false
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// Boolean operations
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!true // false
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!false // true
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true == false // false
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10 > 5 // true
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// Math is as per usual
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1 + 1 // 2
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2 - 1 // 1
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5 * 3 // 15
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6 / 2 // 3
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6 / 4 // 1
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6.0 / 4 // 1.5
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6 / 4.0 // 1.5
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// Evaluating an expression in the REPL gives you the type and value of the result
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1 + 7
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/* The above line results in:
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scala> 1 + 7
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res29: Int = 8
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This means the result of evaluating 1 + 7 is an object of type Int with a
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value of 8
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Note that "res29" is a sequentially generated variable name to store the
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results of the expressions you typed, your output may differ.
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*/
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"Scala strings are surrounded by double quotes"
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'a' // A Scala Char
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// 'Single quote strings don't exist' <= This causes an error
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// Strings have the usual Java methods defined on them
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"hello world".length
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"hello world".substring(2, 6)
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"hello world".replace("C", "3")
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// They also have some extra Scala methods. See also: scala.collection.immutable.StringOps
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"hello world".take(5)
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"hello world".drop(5)
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// String interpolation: notice the prefix "s"
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val n = 45
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s"We have $n apples" // => "We have 45 apples"
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// Expressions inside interpolated strings are also possible
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val a = Array(11, 9, 6)
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s"My second daughter is ${a(0) - a(2)} years old." // => "My second daughter is 5 years old."
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s"We have double the amount of ${n / 2.0} in apples." // => "We have double the amount of 22.5 in apples."
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s"Power of 2: ${math.pow(2, 2)}" // => "Power of 2: 4"
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// Formatting with interpolated strings with the prefix "f"
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f"Power of 5: ${math.pow(5, 2)}%1.0f" // "Power of 5: 25"
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f"Square root of 122: ${math.sqrt(122)}%1.4f" // "Square root of 122: 11.0454"
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// Raw strings, ignoring special characters.
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raw"New line feed: \n. Carriage return: \r." // => "New line feed: \n. Carriage return: \r."
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// Some characters need to be "escaped", e.g. a double quote inside a string:
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"They stood outside the \"Rose and Crown\"" // => "They stood outside the "Rose and Crown""
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// Triple double-quotes let strings span multiple rows and contain quotes
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val html = """<form id="daform">
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<p>Press belo', Joe</p>
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<input type="submit">
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</form>"""
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/////////////////////////////////////////////////
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// 2. Functions
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/////////////////////////////////////////////////
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// Functions are defined like so:
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//
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// def functionName(args...): ReturnType = { body... }
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//
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// If you come from more traditional languages, notice the omission of the
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// return keyword. In Scala, the last expression in the function block is the
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// return value.
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def sumOfSquares(x: Int, y: Int): Int = {
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val x2 = x * x
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val y2 = y * y
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x2 + y2
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}
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// The { } can be omitted if the function body is a single expression:
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def sumOfSquaresShort(x: Int, y: Int): Int = x * x + y * y
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// Syntax for calling functions is familiar:
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sumOfSquares(3, 4) // => 25
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// You can use parameters names to specify them in different order
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def subtract(x: Int, y: Int): Int = x - y
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subtract(10, 3) // => 7
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subtract(y=10, x=3) // => -7
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// In most cases (with recursive functions the most notable exception), function
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// return type can be omitted, and the same type inference we saw with variables
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// will work with function return values:
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def sq(x: Int) = x * x // Compiler can guess return type is Int
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// Functions can have default parameters:
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def addWithDefault(x: Int, y: Int = 5) = x + y
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addWithDefault(1, 2) // => 3
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addWithDefault(1) // => 6
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// Anonymous functions look like this:
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(x: Int) => x * x
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// Unlike defs, even the input type of anonymous functions can be omitted if the
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// context makes it clear. Notice the type "Int => Int" which means a function
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// that takes Int and returns Int.
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val sq: Int => Int = x => x * x
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// Anonymous functions can be called as usual:
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sq(10) // => 100
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// If each argument in your anonymous function is
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// used only once, Scala gives you an even shorter way to define them. These
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// anonymous functions turn out to be extremely common, as will be obvious in
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// the data structure section.
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val addOne: Int => Int = _ + 1
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val weirdSum: (Int, Int) => Int = (_ * 2 + _ * 3)
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addOne(5) // => 6
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weirdSum(2, 4) // => 16
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// The return keyword exists in Scala, but it only returns from the inner-most
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// def that surrounds it.
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// WARNING: Using return in Scala is error-prone and should be avoided.
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// It has no effect on anonymous functions. For example:
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def foo(x: Int): Int = {
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val anonFunc: Int => Int = { z =>
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if (z > 5)
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return z // This line makes z the return value of foo!
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else
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z + 2 // This line is the return value of anonFunc
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}
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anonFunc(x) // This line is the return value of foo
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}
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/////////////////////////////////////////////////
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// 3. Flow Control
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/////////////////////////////////////////////////
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1 to 5
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val r = 1 to 5
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r.foreach(println)
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r foreach println
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// NB: Scala is quite lenient when it comes to dots and brackets - study the
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// rules separately. This helps write DSLs and APIs that read like English
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// Why doesn't `println` need any parameters here?
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// Stay tuned for first-class functions in the Functional Programming section below!
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(5 to 1 by -1) foreach (println)
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// A while loop
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var i = 0
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while (i < 10) { println("i " + i); i += 1 }
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while (i < 10) { println("i " + i); i += 1 } // Yes, again. What happened? Why?
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i // Show the value of i. Note that while is a loop in the classical sense -
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// it executes sequentially while changing the loop variable. while is very
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// fast, but using the combinators and comprehensions above is easier
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// to understand and parallelize
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// A do-while loop
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i = 0
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do {
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println("i is still less than 10")
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i += 1
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} while (i < 10)
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// Recursion is the idiomatic way of repeating an action in Scala (as in most
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// other functional languages).
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// Recursive functions need an explicit return type, the compiler can't infer it.
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// Here it's Unit, which is analagous to a `void` return type in Java
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def showNumbersInRange(a: Int, b: Int): Unit = {
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print(a)
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if (a < b)
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showNumbersInRange(a + 1, b)
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}
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showNumbersInRange(1, 14)
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// Conditionals
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val x = 10
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if (x == 1) println("yeah")
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if (x == 10) println("yeah")
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if (x == 11) println("yeah")
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if (x == 11) println("yeah") else println("nay")
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println(if (x == 10) "yeah" else "nope")
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val text = if (x == 10) "yeah" else "nope"
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/////////////////////////////////////////////////
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// 4. Data Structures
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/////////////////////////////////////////////////
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val a = Array(1, 2, 3, 5, 8, 13)
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a(0) // Int = 1
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a(3) // Int = 5
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a(21) // Throws an exception
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val m = Map("fork" -> "tenedor", "spoon" -> "cuchara", "knife" -> "cuchillo")
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m("fork") // java.lang.String = tenedor
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m("spoon") // java.lang.String = cuchara
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m("bottle") // Throws an exception
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val safeM = m.withDefaultValue("no lo se")
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safeM("bottle") // java.lang.String = no lo se
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val s = Set(1, 3, 7)
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s(0) // Boolean = false
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s(1) // Boolean = true
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/* Look up the documentation of map here -
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* http://www.scala-lang.org/api/current/index.html#scala.collection.immutable.Map
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* and make sure you can read it
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*/
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// Tuples
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(1, 2)
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(4, 3, 2)
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(1, 2, "three")
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(a, 2, "three")
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// Why have this?
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val divideInts = (x: Int, y: Int) => (x / y, x % y)
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// The function divideInts gives you the result and the remainder
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divideInts(10, 3) // (Int, Int) = (3,1)
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// To access the elements of a tuple, use _._n where n is the 1-based index of
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// the element
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val d = divideInts(10, 3) // (Int, Int) = (3,1)
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d._1 // Int = 3
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d._2 // Int = 1
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// Alternatively you can do multiple-variable assignment to tuple, which is more
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// convenient and readable in many cases
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val (div, mod) = divideInts(10, 3)
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div // Int = 3
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mod // Int = 1
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/////////////////////////////////////////////////
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// 5. Object Oriented Programming
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/////////////////////////////////////////////////
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/*
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Aside: Everything we've done so far in this tutorial has been simple
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expressions (values, functions, etc). These expressions are fine to type into
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the command-line interpreter for quick tests, but they cannot exist by
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themselves in a Scala file. For example, you cannot have just "val x = 5" in
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a Scala file. Instead, the only top-level constructs allowed in Scala are:
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- objects
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- classes
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- case classes
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- traits
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And now we will explain what these are.
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*/
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// classes are similar to classes in other languages. Constructor arguments are
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// declared after the class name, and initialization is done in the class body.
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class Dog(br: String) {
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// Constructor code here
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var breed: String = br
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// Define a method called bark, returning a String
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def bark = "Woof, woof!"
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// Values and methods are assumed public. "protected" and "private" keywords
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// are also available.
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private def sleep(hours: Int) =
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println(s"I'm sleeping for $hours hours")
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// Abstract methods are simply methods with no body. If we uncomment the
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// def line below, class Dog would need to be declared abstract like so:
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// abstract class Dog(...) { ... }
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// def chaseAfter(what: String): String
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}
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val mydog = new Dog("greyhound")
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println(mydog.breed) // => "greyhound"
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println(mydog.bark) // => "Woof, woof!"
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|
||||
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||||
// The "object" keyword creates a type AND a singleton instance of it. It is
|
||||
// common for Scala classes to have a "companion object", where the per-instance
|
||||
// behavior is captured in the classes themselves, but behavior related to all
|
||||
// instance of that class go in objects. The difference is similar to class
|
||||
// methods vs static methods in other languages. Note that objects and classes
|
||||
// can have the same name.
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object Dog {
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def allKnownBreeds = List("pitbull", "shepherd", "retriever")
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def createDog(breed: String) = new Dog(breed)
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}
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// Case classes are classes that have extra functionality built in. A common
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||||
// question for Scala beginners is when to use classes and when to use case
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||||
// classes. The line is quite fuzzy, but in general, classes tend to focus on
|
||||
// encapsulation, polymorphism, and behavior. The values in these classes tend
|
||||
// to be private, and only methods are exposed. The primary purpose of case
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||||
// classes is to hold immutable data. They often have few methods, and the
|
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// methods rarely have side-effects.
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case class Person(name: String, phoneNumber: String)
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// Create a new instance. Note cases classes don't need "new"
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val george = Person("George", "1234")
|
||||
val kate = Person("Kate", "4567")
|
||||
|
||||
// With case classes, you get a few perks for free, like getters:
|
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george.phoneNumber // => "1234"
|
||||
|
||||
// Per field equality (no need to override .equals)
|
||||
Person("George", "1234") == Person("Kate", "1236") // => false
|
||||
|
||||
// Easy way to copy
|
||||
// otherGeorge == Person("George", "9876")
|
||||
val otherGeorge = george.copy(phoneNumber = "9876")
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||||
|
||||
// And many others. Case classes also get pattern matching for free, see below.
|
||||
|
||||
// Traits
|
||||
// Similar to Java interfaces, traits define an object type and method
|
||||
// signatures. Scala allows partial implementation of those methods.
|
||||
// Constructor parameters are not allowed. Traits can inherit from other
|
||||
// traits or classes without parameters.
|
||||
|
||||
trait Dog {
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||||
def breed: String
|
||||
def color: String
|
||||
def bark: Boolean = true
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||||
def bite: Boolean
|
||||
}
|
||||
class SaintBernard extends Dog {
|
||||
val breed = "Saint Bernard"
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||||
val color = "brown"
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||||
def bite = false
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||||
}
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||||
scala> b
|
||||
res0: SaintBernard = SaintBernard@3e57cd70
|
||||
scala> b.breed
|
||||
res1: String = Saint Bernard
|
||||
scala> b.bark
|
||||
res2: Boolean = true
|
||||
scala> b.bite
|
||||
res3: Boolean = false
|
||||
|
||||
// A trait can also be used as Mixin. The class "extends" the first trait,
|
||||
// but the keyword "with" can add additional traits.
|
||||
|
||||
trait Bark {
|
||||
def bark: String = "Woof"
|
||||
}
|
||||
trait Dog {
|
||||
def breed: String
|
||||
def color: String
|
||||
}
|
||||
class SaintBernard extends Dog with Bark {
|
||||
val breed = "Saint Bernard"
|
||||
val color = "brown"
|
||||
}
|
||||
|
||||
scala> val b = new SaintBernard
|
||||
b: SaintBernard = SaintBernard@7b69c6ba
|
||||
scala> b.bark
|
||||
res0: String = Woof
|
||||
|
||||
|
||||
/////////////////////////////////////////////////
|
||||
// 6. Pattern Matching
|
||||
/////////////////////////////////////////////////
|
||||
|
||||
// Pattern matching is a powerful and commonly used feature in Scala. Here's how
|
||||
// you pattern match a case class. NB: Unlike other languages, Scala cases do
|
||||
// not need breaks, fall-through does not happen.
|
||||
|
||||
def matchPerson(person: Person): String = person match {
|
||||
// Then you specify the patterns:
|
||||
case Person("George", number) => "We found George! His number is " + number
|
||||
case Person("Kate", number) => "We found Kate! Her number is " + number
|
||||
case Person(name, number) => "We matched someone : " + name + ", phone : " + number
|
||||
}
|
||||
|
||||
// Regular expressions are also built in.
|
||||
// Create a regex with the `r` method on a string:
|
||||
val email = "(.*)@(.*)".r
|
||||
|
||||
// Pattern matching might look familiar to the switch statements in the C family
|
||||
// of languages, but this is much more powerful. In Scala, you can match much
|
||||
// more:
|
||||
def matchEverything(obj: Any): String = obj match {
|
||||
// You can match values:
|
||||
case "Hello world" => "Got the string Hello world"
|
||||
|
||||
// You can match by type:
|
||||
case x: Double => "Got a Double: " + x
|
||||
|
||||
// You can specify conditions:
|
||||
case x: Int if x > 10000 => "Got a pretty big number!"
|
||||
|
||||
// You can match case classes as before:
|
||||
case Person(name, number) => s"Got contact info for $name!"
|
||||
|
||||
// You can match regular expressions:
|
||||
case email(name, domain) => s"Got email address $name@$domain"
|
||||
|
||||
// You can match tuples:
|
||||
case (a: Int, b: Double, c: String) => s"Got a tuple: $a, $b, $c"
|
||||
|
||||
// You can match data structures:
|
||||
case List(1, b, c) => s"Got a list with three elements and starts with 1: 1, $b, $c"
|
||||
|
||||
// You can nest patterns:
|
||||
case List(List((1, 2, "YAY"))) => "Got a list of list of tuple"
|
||||
|
||||
// Match any case (default) if all previous haven't matched
|
||||
case _ => "Got unknown object"
|
||||
}
|
||||
|
||||
// In fact, you can pattern match any object with an "unapply" method. This
|
||||
// feature is so powerful that Scala lets you define whole functions as
|
||||
// patterns:
|
||||
val patternFunc: Person => String = {
|
||||
case Person("George", number) => s"George's number: $number"
|
||||
case Person(name, number) => s"Random person's number: $number"
|
||||
}
|
||||
|
||||
|
||||
/////////////////////////////////////////////////
|
||||
// 7. Functional Programming
|
||||
/////////////////////////////////////////////////
|
||||
|
||||
// Scala allows methods and functions to return, or take as parameters, other
|
||||
// functions or methods.
|
||||
|
||||
val add10: Int => Int = _ + 10 // A function taking an Int and returning an Int
|
||||
List(1, 2, 3) map add10 // List(11, 12, 13) - add10 is applied to each element
|
||||
|
||||
// Anonymous functions can be used instead of named functions:
|
||||
List(1, 2, 3) map (x => x + 10)
|
||||
|
||||
// And the underscore symbol, can be used if there is just one argument to the
|
||||
// anonymous function. It gets bound as the variable
|
||||
List(1, 2, 3) map (_ + 10)
|
||||
|
||||
// If the anonymous block AND the function you are applying both take one
|
||||
// argument, you can even omit the underscore
|
||||
List("Dom", "Bob", "Natalia") foreach println
|
||||
|
||||
|
||||
// Combinators
|
||||
// Using `s` from above:
|
||||
// val s = Set(1, 3, 7)
|
||||
|
||||
s.map(sq)
|
||||
|
||||
val sSquared = s. map(sq)
|
||||
|
||||
sSquared.filter(_ < 10)
|
||||
|
||||
sSquared.reduce (_+_)
|
||||
|
||||
// The filter function takes a predicate (a function from A -> Boolean) and
|
||||
// selects all elements which satisfy the predicate
|
||||
List(1, 2, 3) filter (_ > 2) // List(3)
|
||||
case class Person(name: String, age: Int)
|
||||
List(
|
||||
Person(name = "Dom", age = 23),
|
||||
Person(name = "Bob", age = 30)
|
||||
).filter(_.age > 25) // List(Person("Bob", 30))
|
||||
|
||||
|
||||
// Certain collections (such as List) in Scala have a `foreach` method,
|
||||
// which takes as an argument a type returning Unit - that is, a void method
|
||||
val aListOfNumbers = List(1, 2, 3, 4, 10, 20, 100)
|
||||
aListOfNumbers foreach (x => println(x))
|
||||
aListOfNumbers foreach println
|
||||
|
||||
// For comprehensions
|
||||
|
||||
for { n <- s } yield sq(n)
|
||||
|
||||
val nSquared2 = for { n <- s } yield sq(n)
|
||||
|
||||
for { n <- nSquared2 if n < 10 } yield n
|
||||
|
||||
for { n <- s; nSquared = n * n if nSquared < 10} yield nSquared
|
||||
|
||||
/* NB Those were not for loops. The semantics of a for loop is 'repeat', whereas
|
||||
a for-comprehension defines a relationship between two sets of data. */
|
||||
|
||||
|
||||
/////////////////////////////////////////////////
|
||||
// 8. Implicits
|
||||
/////////////////////////////////////////////////
|
||||
|
||||
/* WARNING WARNING: Implicits are a set of powerful features of Scala, and
|
||||
* therefore it is easy to abuse them. Beginners to Scala should resist the
|
||||
* temptation to use them until they understand not only how they work, but also
|
||||
* best practices around them. We only include this section in the tutorial
|
||||
* because they are so commonplace in Scala libraries that it is impossible to
|
||||
* do anything meaningful without using a library that has implicits. This is
|
||||
* meant for you to understand and work with implicits, not declare your own.
|
||||
*/
|
||||
|
||||
// Any value (vals, functions, objects, etc) can be declared to be implicit by
|
||||
// using the, you guessed it, "implicit" keyword. Note we are using the Dog
|
||||
// class from section 5 in these examples.
|
||||
implicit val myImplicitInt = 100
|
||||
implicit def myImplicitFunction(breed: String) = new Dog("Golden " + breed)
|
||||
|
||||
// By itself, implicit keyword doesn't change the behavior of the value, so
|
||||
// above values can be used as usual.
|
||||
myImplicitInt + 2 // => 102
|
||||
myImplicitFunction("Pitbull").breed // => "Golden Pitbull"
|
||||
|
||||
// The difference is that these values are now eligible to be used when another
|
||||
// piece of code "needs" an implicit value. One such situation is implicit
|
||||
// function arguments:
|
||||
def sendGreetings(toWhom: String)(implicit howMany: Int) =
|
||||
s"Hello $toWhom, $howMany blessings to you and yours!"
|
||||
|
||||
// If we supply a value for "howMany", the function behaves as usual
|
||||
sendGreetings("John")(1000) // => "Hello John, 1000 blessings to you and yours!"
|
||||
|
||||
// But if we omit the implicit parameter, an implicit value of the same type is
|
||||
// used, in this case, "myImplicitInt":
|
||||
sendGreetings("Jane") // => "Hello Jane, 100 blessings to you and yours!"
|
||||
|
||||
// Implicit function parameters enable us to simulate type classes in other
|
||||
// functional languages. It is so often used that it gets its own shorthand. The
|
||||
// following two lines mean the same thing:
|
||||
// def foo[T](implicit c: C[T]) = ...
|
||||
// def foo[T : C] = ...
|
||||
|
||||
|
||||
// Another situation in which the compiler looks for an implicit is if you have
|
||||
// obj.method(...)
|
||||
// but "obj" doesn't have "method" as a method. In this case, if there is an
|
||||
// implicit conversion of type A => B, where A is the type of obj, and B has a
|
||||
// method called "method", that conversion is applied. So having
|
||||
// myImplicitFunction above in scope, we can say:
|
||||
"Retriever".breed // => "Golden Retriever"
|
||||
"Sheperd".bark // => "Woof, woof!"
|
||||
|
||||
// Here the String is first converted to Dog using our function above, and then
|
||||
// the appropriate method is called. This is an extremely powerful feature, but
|
||||
// again, it is not to be used lightly. In fact, when you defined the implicit
|
||||
// function above, your compiler should have given you a warning, that you
|
||||
// shouldn't do this unless you really know what you're doing.
|
||||
|
||||
|
||||
/////////////////////////////////////////////////
|
||||
// 9. Misc
|
||||
/////////////////////////////////////////////////
|
||||
|
||||
// Importing things
|
||||
import scala.collection.immutable.List
|
||||
|
||||
// Import all "sub packages"
|
||||
import scala.collection.immutable._
|
||||
|
||||
// Import multiple classes in one statement
|
||||
import scala.collection.immutable.{List, Map}
|
||||
|
||||
// Rename an import using '=>'
|
||||
import scala.collection.immutable.{List => ImmutableList}
|
||||
|
||||
// Import all classes, except some. The following excludes Map and Set:
|
||||
import scala.collection.immutable.{Map => _, Set => _, _}
|
||||
|
||||
// Java classes can also be imported. Scala syntax can be used
|
||||
import java.swing.{JFrame, JWindow}
|
||||
|
||||
// Your programs entry point is defined in a scala file using an object, with a
|
||||
// single method, main:
|
||||
object Application {
|
||||
def main(args: Array[String]): Unit = {
|
||||
// stuff goes here.
|
||||
}
|
||||
}
|
||||
|
||||
// Files can contain multiple classes and objects. Compile with scalac
|
||||
|
||||
|
||||
|
||||
|
||||
// Input and output
|
||||
|
||||
// To read a file line by line
|
||||
import scala.io.Source
|
||||
for(line <- Source.fromFile("myfile.txt").getLines())
|
||||
println(line)
|
||||
|
||||
// To write a file use Java's PrintWriter
|
||||
val writer = new PrintWriter("myfile.txt")
|
||||
writer.write("Writing line for line" + util.Properties.lineSeparator)
|
||||
writer.write("Another line here" + util.Properties.lineSeparator)
|
||||
writer.close()
|
||||
|
||||
```
|
||||
|
||||
## Further resources
|
||||
|
||||
* [Scala for the impatient](http://horstmann.com/scala/)
|
||||
* [Twitter Scala school](http://twitter.github.io/scala_school/)
|
||||
* [The scala documentation](http://docs.scala-lang.org/)
|
||||
* [Try Scala in your browser](http://scalatutorials.com/tour/)
|
||||
* Join the [Scala user group](https://groups.google.com/forum/#!forum/scala-user)
|
||||
Loading…
Reference in New Issue
Block a user