scala in action

Implicit is a very important feature in Scala and has been thinking about it as much as Java before starting to learn Scala, but it's not as easy to see some of Scala's source code as it is, so I'm going to write a few articles to explain the features of Scala that are different from Java. Implicit, let's get started. In my opinion, what implicit do is also the m

Scala Language Basics 1. Scala morphology The character set used by the Scala program is the basic Multilingual plane character set for Unicode, and the following defines the two modes of Scala morphology: Scala mode and XML schema. If not specifically stated, the foll

The existing Scala bookcase include: Programming in Scala. The masterpieces of the Scala creator, Martin Ordersky, are the most authoritative of Scala's introductory bookcase, but the Scala version of the book is a bit old, and the whole book gives me a feeling that it's just a few examples of things that don't fe

conversion to ArrayOps is temporary, as all operations defined on ArrayOps return an Array, while the conversion to WrappedArray is permanent as all operations return a WrappedArray.Case two: Pairrddfunctions type enhancements to RDD in sparkIf you look at the RDD in Spark and its subclasses are not Groupbykey, Reducebykey, and join-based operations of Key-value tuples, but when you use the RDD, these operations are real, It is the implicit conversion of spark that transforms an rdd into a pair

Key points in this chapter All collections are extended from iterable traits There are three main classes of collections: sequence, set, map Scala provides both mutable and immutable versions for almost all collection classes The Scala list is either empty or has a tail, where the trailer itself is a list Set is a set of no precedence Use Linkedhashset to preserve the insertion

variables, such as (x: Int) => x + 1 , are called closed items (closed term). Therefore, the function value created at run time according to this function literal is not strictly a closure, because (x: Int) => x + 1 it is closed at the time of writing. But any function literal with free variables, such as (x: Int) => x + more , is open term. Therefore, any (x: Int) => x + more function value created for the template re-run will have to capture the binding to the free variable more . The resulti

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 + more//How much is it? function to add "more" to the reference, but what is more? From the point of view of this function, more is a free variable: variable, because the function text itself does not gi

master constructor to initialize objects. The definition of the constructor starts with Def this. For example, if the default weight of fruit is 10. class Fruit(n: String, w: Int) { val name = n val weight = w println("This is a " + n) println("Weight = " + w) def this(n: String) = this(n, 10)} val orange = Fruit("Orange") The slave constructor on Scala also has certain limitations, which is written in Scala