Shulou(Shulou.com)06/03 Report--

A good programmer big data tutorial Scala series sample class_Option_partial function, in Scala Option type sample class is used to represent values that may or may not exist (Option subclasses are Some and None). Some wraps a value, None means no value.

object OptionDemo {

def main(args: Array[String]) {

val map = Map("a" -> 1, "b" -> 2)

val v = map.get("b") match {

case Some(i) => i

case None => 0

}

println(v)

A better way.

val v1 = map.getOrElse("c", 0)

println(v1)

}

}

partial function

A set of case statements enclosed in braces without a match is a partial function, which is an instance of PartialFunction[A, B], where A represents the parameter type and B represents the return type, often used as input pattern matching.

object PartialFunctionDemo {

def f: PartialFunction[String, Int] = {

case "one" => 1

case "two" => 2

// case _ => -1

}

def main(args: Array[String]) {

//call f.apply("one")

println(f("one"))

println(f.isDefinedAt("three"))

//MatchError thrown

println(f("three"))

}

}String INTERPOLATION(optional)

Purpose: Processing String Type:

s: string interpolation

f: Interpolate and format output

raw: output without any transformation of the string

After Scala 2.10.0, a new mechanism for creating strings was introduced, namely String Interpolation. It allows users to embed references to variables directly in strings.

val name="James"

println(s"Hello,$name") // Hello, James

A string interpolation can also be placed in an expression, as follows:

println(s"1 + 1 = ${1 + 1}")// 1 + 1 = 2

Interpolation f can format strings, similar to printf:

val height = 1.9d

val name = "James"

println(f"$name%s is $height%2.2f meters tall") // James is 1.90 meters tall

raw is similar to s, but raw does not convert string contents:

scala> s"a\nb"

res0: String =

a

b

scala> raw"a\nb"

res1: String = a\nb

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