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:: Appends the object to the head of the list.The head part of an existing list[subclass X] is placed in another object A, which is a subclass Y, and if both a object and the original list object inherit from the same parent class, the list is displayed as the list[parent class].The parameters of the function are contravariant so that covariance cannot occur, so the nether is used to solve the problem. The object to which the:: Method returns is programmed as a list of upper bound object B.inter

Package Com.dt.scala.listObject Listbuffer_internals {def main (args:array[string]) {Val list = list (1,2,3,4,5,6,7,8,9)Increment (list)Increment_moreeffective (list)Increment_mosteffective (list)}def increment (List:list[int]): list[int] = list match {Case list () = List ()Case HEAD:: tail = head + 1:: Increment (tail)}def increment_moreeffective (List:list[int]): list[int] = {var result = List[int] ()for (element Result}def increment_mosteffective (List:list[int]): list[int] = {Import Scala.co

Default value:def saymyname (name:string = "Jack") {println (name)}Variable parameters:def summoreparameters (elem:int*) = { var sum = 0for (e Use of underscores:def add (a:int,b:int) = a+bdef add2 = Add (_:int,2)Recursive functions: Need to explicitly give the return type of the functiondef FAC (n:int): Int = if (n function currying:Write this argument independently, this is curryingdef mulitply (X:int) (y:int) = x*ydef m2 = mulitply (2) _;Curry is the parameter can be separated, some of the

From Scala wizard Chapter 1 functional objects With the basic Scala knowledge gained from the previous chapters, you are ready to explore how to design objects with more comprehensive features in Scala. This chapter focuses on defining functional objects, that is, classes of objects without any variable states. As an example of running, we will create several Cl

Scala basic syntax If you have a good understanding of the Java language, it will be easy to learn Scala. The most important difference between Scala and Java is that the line terminator is optional. Consider a Scala program that can be defined as a collection of objects that communicate by calling each other's methods

addition, you can also get conversions from java.util.Properties to map[string,string] :Import Scala.collection.JavaConversions.propertiesAsScalaMapVal props: scala.collection.map[string, String] = System.getproperties ()Scala to JavaConversely, to pass the Scala mapping to the intended Java mapping method, provide the opposite implicit conversionFor example:Import Scala.collection.JavaConversions.mapAsjav

use the + and-operations for an immutable map, but a new map is generated. VaR map = map ("AA"-> 1) Map = map + ("BB"-> 2) MAP + = ("cc"-> 2) Map-= "AA"Iterative map: For (K, v) // Todo } All keys: Map. keyset All values: Map. Values Reverse: MAP2 = for (K, v) Sorted map: Sort by key: Sortedmap Add order: LinkedhashmapMap and Java interoperability: Convert Java properties to Scala. collection. MAP: Import scala