bookinstock/cheatsheet

cheatsheet

scala

• It’s a high-level language

• It’s statically typed

• Its syntax is concise but still readable — we call it expressive

• It supports the object-oriented programming (OOP) paradigm

• It supports the functional programming (FP) paradigm

• It has a sophisticated type inference system

• Scala code results in .class files that run on the Java Virtual Machine (JVM)

• It’s easy to use Java libraries in Scala

• Strings and built-in numeric types

• Packaging and imports

• How to use Java collections classes in Scala

• How to use Java libraries in Scala

• How to build Scala projects

• How to perform unit testing in Scala

• How to write Scala shell scripts

• Maps, Sets, and other collections classes

• Object-oriented programming

• Functional programming

• Concurrency with Futures

• More …

collection

0 to 10 by 2

1 to 2 contains 2

for

for e <- seq {}

for e <- seq if xx {}

for e <- seq yield {}

foreach

map

filter

pattern match

def fn(x: Any): String = x match { case 1 => "one" case 2 | 3 => "two or three" case v if v < 5 => "four" case v: String => s"str $v" case _ => "?" }

future

• You construct futures to run tasks off of the main thread
• Futures are intended for one-shot, potentially long-running concurrent tasks that eventually return a value
• A future starts running as soon as you construct it
• A benefit of futures over threads is that they come with a variety of callback methods that simplify the process of working with concurrent threads, including the handling of exceptions and thread management
• Handle the result of a future with methods like onComplete, or combinator methods like map, flatMap, filter, andThen, etc.
• The value in a Future is always an instance of one of the Try types: Success or Failure
• If you’re using multiple futures to yield a single result, you’ll often want to combine them in a for-expression