yes scala can!
DESCRIPTION
The presentation I had for Stockholm Knowledge Network. For demo code please refer to https://github.com/anderseriksson/yesscalacanTRANSCRIPT
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The place for sharing ideas and knowledge
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Yes Scala Can!
Amir Moulavi Anders Eriksson @mamirm @anders_eriksson [email protected] [email protected]
Jayway Stockholm2012-05-30
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Why
● We've found Scala and like it! ● We would like to broaden the interest
amongst Java developers. ● Hopefully this presentation will inspire you to
look more into Scala!
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Agenda
● History and Background ● Scala vs. Java: Similarities and Differences ● Quick Journey to Scala ● Book Raffle!
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It has been a revolution!
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Little history and background
● 2001: ○ Design of Scala started
■ Goals: merge functional + object oriented paradigms
● 2004:○ First public release on JVM
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Little history and background
● 2006:○ major rewrite (v 2.0)
● 2011:
○ Company Typesafe is funded for professional support
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Java vs. Scala (similarities)
● Runs on JVM ● Statically typed ● Object oriented ● Garbage collected
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Java vs. Scala (differences)
● Pure object orientation ● Functional paradigm ● Pattern matching ● Mixin composition
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Java vs. Scala (differences)
● No checked exception ● Implicit conversions ● Flexible imports and access modifier ● Read Evaluate Print Loop (REPL) console
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Scala is a unifier
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Scala is Object-oriented
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Scala is Functional
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Scala is statically typed
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Scala is concisepublic class Person {
private final String name;
private final int age;
public Person(String name, int age) {
this.name = name;
this.int = int;
}
public String getName() {return name;
}
public int getAge() {
return age;
}}
Java
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Scala is conciseclass Person(val name:String, val age:Int)
Scala
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Scala is expressive (1 to 10) filter (_ > 7)
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REPL
The command line for Scala
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Tuples
( , )( , , )( , , , )( , , , , )( , , , , , )
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Tuples
● Saves you the tedium of defining simplistic data-heavy classes
● Immutable ● Each value different type ● Can contain up to 22 values ● Indexed from 1
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REPL and Tuples
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Case classes
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Case classes
● Easier instantiation ● Immutability in constructor parameters by
default ● You get these methods for free
○ toString()○ equals()○ hashCode()○ apply()○ copy()
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Case classes
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Pattern Matching
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Pattern Matching
● Similar to Java's switch statement ● Let you match any sort of data ● First-match policy
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Pattern Matching
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Higher Order Functions
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Higher Order Functions
● Functions are first class citizens in Scala
F : A B ● Higher Order Functions are functions that
take functions as input parameters or return them as results
F : (A B) (R S)
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Higher Order Functions
map(f) filter(f)
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Powerful Collections
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Powerful Collections
● Easy to use
○ A small vocabulary of 20-50 methods to solve most collection problems
● Concise
○ A single word instead of several loops!
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Powerful Collections
● Safe○ Functional nature + Statically typed!
● Fast
○ Tuned and optimized collections' operations ● Universal
○ The same operation on any type
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Powerful Collections
Scala Collections
MutableImmutable
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Powerful Collections
● List○ Immutable and ListBuffer is mutable
● Array ○ Mutable
● Set○ Immutable and mutable
● Map○ Immutable and mutable
● ... and String!○
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Powerful Collections with Higher Order Functions
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Traits
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Traits
● Definition:
○ Provides a set of methods that implement behaviour
○ Requires a set of methods that parameterized the
provided behaviour ○ Does not specify any state variables
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Traits
● Interfaces with behaviors ● Fundamental unit of code re-use ● Extremely powerful tool in OO design
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Traits
Rich interfaces
Stackable modifications
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Traits
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Parallel Collections
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Parallel Collections
● Supports the same operations as sequential ones
● Easily convert sequential to parallel
collection
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Parallel Collections
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Scala and Java Integration
● Seamless integration ● Make full use of existing libraries and code
Scala Java
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Scala and Java Integration
● Familiar development environments○ Eclipse, IntelliJ, Netbeans, ...
● Familiar building tools like Maven
○ SBT ● If you are a Java developer, you're halfway
there!
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What's Scala advantage over Java as a language choice?
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● implicit parameters● pattern matching● case classes● type inferencing● higher-kinded types● monadic for comprehension● variance annotation● traits● default and named argument● abstract values● by-name terms● type aliasing● self types● path-dependent types● structural types● ...
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Conclusion
● Scala is not complex ● Express your ideas in a concise way ● Better code readability ● Scala = Functional + Object oriented
paradigms. ● Scala scales with programmers
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Where to go from here?
Programming in Scala, 2nd edition by Martin Odersky, Lex Spoon andBill Venners Scala for the Impatient byCay Hortsmann
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Where to go from here?
Scala Stockholm User Group http://www.meetup.com/Scala-Stockholm/
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Where to go from here?
Scala course "Fast-Track to Scala" from Typesafe 18-19 September, 2012
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Where to go from here?
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Questions?
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Thank you!
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The place for sharing ideas and knowledge