深入理解Scala编程：权威指南

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ACKNOWLEDGMENTS xv

discussing the type system and implicit resolution and helped make the discussions

both practical and correct. Eric Weinberg was an old coworker of mine who helped

provide guidance for reaching non-Scala developers in the book. Viktor Klang

reviewed the “Actors” chapter (and the whole book) and offered improvements.

Thank you also to Martin Odersky for his endorsement and kind words on the final

product that you will read in the foreword, Josh Cough for being a guy I can bounce

ideas off when needed, and Peter Simanyi for an email with a very detailed, thorough,

complete, and awesome review of the entire book.

Manning also contacted the following reviewers, who read the manuscript at vari-

ous stages of its development, and I would like to thank them for their invaluable

insights and comments: John C. Tyler, Orhan Alkan, Michael Nash, John Griffin,

Jeroen Benckhuijsen, David Biesack, Lutz Hankewitz, Oleksandr Alesinskyy, Cheryl

Jerozal, Edmon Begoli, Ramnivas Laddad, Marco Ughetti, Marcus Kazmierczak, Ted

Neward, Eric Weinberg, Dave Pawson, Patrick Steger, Paul Stusiak, Mark Thomas,

David Dossot, Tariq Ahmed, Ken McDonald, Mark Needham, and James Hatheway.

Finally, I’d like to thank all of the MEAP reviewers. I received great feedback from

them and appreciate the support and good reviews this book received before it was

even in print. You guys had to bear with lots of typos and errors and deserve credit for

persevering through my rough initial cuts and making it to this final version.

ABOUT THIS BOOK xvii

Chapter 2 is a discussion of the core rules of Scala. These are the things that every

Scala developer should be aware of and make use of in daily development. This chap-

ter is for every Scala developer and covers the basics that make Scala a great language.

Chapter 3 is a digression in code style and associated issues. Scala brings a few new

players to the table, and any Scala style guide should reflect that. Some common con-

ventions from popular languages like Ruby and Java can actually be deterrents to

good Scala code.

Chapter 4 covers new issues arising in object-oriented design due to Scala’s mixin

inheritance. One topic of interest to any Scala developer is the early initializer cover-

age, which gets little coverage in other books.

After object orientation, the book moves into the implicit system. In chapter 5,

rather than simply discussing best practices, a deep dive is taken into the mechanics of

implicits in Scala. This chapter is a must for all Scala developers who wish to write

expressive libraries and code.

Chapter 6 is devoted to Scala’s type system. The discussion covers all the ways

types appear in Scala and how to utilize the type system to enforce constraints. The

chapter moves into a discussion of higher-kinded types and finishes with a dive into

existential types.

Chapter 7 discusses the most advanced usage patterns in the language, the inter-

section of types and implicits. This intersection is where a lot of interesting and power-

ful abstractions occur, the epitome of which is the type class pattern.

Having covered the most advanced aspects of Scala, in chapter 8 we move into a

discussion of Scala’s collection library. This includes the design and performance of

Scala’s collections as well as how to deal with the powerful type mechanisms.

Chapter 9 kicks off the discussion on actors in Scala. Actors are a concurrency

mechanism that can provide great throughput and parallelism when used appropri-

ately. The chapter dives into issues of designing actor-based systems and finishes with a

demonstration of how the Akka actors library provides best practices by default.

Chapter 10 covers Java integration with Scala. While Scala is more compatible with

Java than most other

JVM languages, there’s still a mismatch in features between the

two. It’s at these corners that issues arise in Scala-Java integration and this chapter pro-

vides a few simple rules that help avoid these issues.

Chapter 11 takes concepts from category theory and makes them practical. In pure

functional programming, a lot of concepts from category theory have been applied to

code. These are akin to object-oriented design patterns, but far more abstract. While

they have terrible names, as is common in mathematics, these concepts are immensely

useful in practice. No coverage of functional programming would be complete with-

out a discussion of some of these abstractions, and Scala in Depth does its best to

make these concepts real.

Code downloads and conventions

All source code in the book is in a

fixed-width

font

this

, which sets it off from

the surrounding text. In many listings, the code is annotated to point out the key

ABOUT THIS BOOKxviii

concepts. I have tried to format the code so that it fits within the available page space

in the book by adding line breaks and using indentation carefully. Sometimes, how-

ever, very long lines include line-continuation markers.

Source code for all the working examples is available from www.manning.com/

ScalainDepth and at https://github.com/jsuereth/scala-in-depth-source. To run the

examples, readers should have Scala installed and, optionally, SBT (http://scala-

sbt.org).

Code examples appear throughout this book. Longer listings appear under clear

listing headers; shorter listings appear between lines of text.

Author online

Purchase of Scala in Depth includes free access to a private web forum run by Manning

Publications where you can make comments about the book, ask technical questions,

and receive help from the authors and from other users. To access the forum and sub-

scribe to it, point your web browser to www.manning.com/ScalainDepth. This page

provides information on how to get on the forum once you’re registered, what kind of

help is available, and the rules of conduct on the forum.

Manning’s commitment to our readers is to provide a venue where a meaningful

dialog between individual readers and between readers and the authors can take

place. It’s not a commitment to any specific amount of participation on the part of the

authors, whose contribution to the AO forum remains voluntary (and unpaid). We

suggest you try asking the author some challenging questions lest his interest stray.

The Author Online forum and the archives of previous discussions will be accessi-

ble from the publisher’s website as long as the book is in print.

About the author

Josh Suereth is a Senior Software Engineer at Typesafe Inc., the company behind

Scala. He has been a Scala enthusiast since he came to know this beautiful language in

2007. He started his professional career as a software developer in 2004, cutting his

teeth with C++, STL, and Boost. Around the same time, Java fever was spreading and

his interest was migrating to web-hosted distributed Java-delivered solutions to aid

health departments in the discovery of disease outbreaks.

He introduced Scala into his company code base in 2007, and soon after he was

infected by Scala fever, contributing to the Scala IDE, maven-scala-plugin and Scala

itself. Today, Josh is the author of several open source Scala projects, including the

Scala automated resource management library and the PGP sbt plugin, as well as con-

tributing to key components in the Scala ecosystem, like the maven-scala-plugin. His

current work at Typesafe Inc., has him doing everything from building MSIs to profil-

ing performance issues.

Josh regularly shares his expertise in articles and talks. He likes short walks on the

beach and dark beer.

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深入理解Scala编程：权威指南

Scala in Depth

scala.xml.XML

import scala.collection中collection飘红

程序包scala.collection不存在

java.lang.ClassNotFoundException: scala.collection.Seq

scala 引用java list_如何在Java代码中使用scala.collection.immutable.List

Caused by: java.lang.ClassNotFoundException: scala.collection.mutable.ArraySeq$ofRef

如何解决scala.MatchError: WrappedArray(947,106, 812,366) (of class scala.collection.mutable.WrappedArray$ofRef)

java.lang.ClassCastException: cannot assign instance of scala.collection.immutable.List$SerializationProxy to field org.apache.spark.rdd.RDD.org$apache$spark$rdd$RDD$$dependencies_ of type scala.collection.Seq in instance of org.apache.spark.rdd.MapPartitionsRDD

Caused by: java.lang.ClassNotFoundException: scala.Cloneable

visual studio code scala not found scala.util.Random 如何解决

java.lang.NoSuchMethodError: scala.Predef$.refArrayOps([Ljava/lang/Object;)Lscala/collection/mutable/ArrayOps

尚硅谷大数据技术之scala.docx

Caused by: java.lang.ClassNotFoundException: scala.Serializable

spark sql执行报错java.lang.ClassNotFoundException: scala.jdk.CollectionConverters$

出现了 ERROR:scala:Error:Object scala.runtime in compiler mirror not found 怎么解决

val res9: String = scala.collection.immutable.$colon$colon

exception in thread "main" java.lang.nosuchmethoderror: scala.util.matching.regex.<init>(ljava/lang/string;lscala/collection/seq;)v

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