Some useful Scala examples

Language constructs

Hello World

• Hello World with main method
• Hello World without main method

Common Keywords

• Usage of 'import' to import classes
• Usage of 'tuple' to build abstractions over related values
• Usage of 'yield' in extracting values during loops
• Usage of 'isInstanceOf'
• Usage of 'try' 'catch'
• Usage of 'require' to enforce restrictions before creating instance of a Scala class
• Usage of 'tailrec' during recursions in methods
• Usage of keyword '++' in collections
• Usage of 'Either' as return types
• Usage of '@inline' as performance optimizer

Basic Constructs: trait, class, object, annotations

• Java 'Object' is equivalent to Scala 'AnyRef'
• Java 'void' is equivalent to Scala 'Unit'
• Java 'enum' is equivalent to Scala 'sealed trait'
• Java 'interface' is equivalent to Scala 'trait'
• Purpose of trait, class and Object keywords in Scala
• "Hello"(4) is actually "Hello".apply(4)
• Create custom annotations using 'scala.annotation.StaticAnnotation'
• The 'App' trait can be used to quickly turn objects into executable programs

Var, Val, Int, Float, Double, BigInteger

• Various Scala types
• Values which are lazy initialised using 'lazy val'
• BigInt("1234567890") is actually BigInt.apply("1234567890")

Looping

• Different types of looping techniques
• Usage of 'for each' as loop

Methods/Functions

• How methods or definitions are created using 'def'
• How object-private access works
• How definitions can also be created using 'var' or 'val'
• Type aliases in Scala
• Never use 'return' keyword in Scala method
• A function without a return type is called Procedure in Scala
• Example of a function that can take a variable number of arguments
• Difference between call by name and call by value
• Methods 'apply' as Injector and 'unapply' as Extractor
• Operators are nothing just methods. Operator overloading example

Collection

• Usage of 'Seq[String]' in Scala
• Usage of 'List' and 'Vector' in Scala
• Usage of 'ArrayBuffer' in Scala
• Usage of WeakHashMap in Scala
• Different operations on List class
• Scala Array that can store all object types
• Equivalent of Java 'ArrayList' Class in Scala is 'ArrayBuffer'

Others

• How Scala beans works : Half a line of Scala is the equivalent of seven lines of Java
• Primary constructor
• Auxiliary constructors
• Difference between private and private[this]
• Value '_' initializes to default value of variable
• How getter/setter is automatically generated in a class
• How Scala avoids NullPointerException using 'Option', 'Some' and 'None'
• Default object factory in Scala
• [Using 'strip margin' to add new lines in string][CustomerRestService.md]
• Generics example
• Enviornment variables example
• How to find object hashcode in Scala
• How to view bounds works in Scala
• How to upper and lower type bounds works in Scala

Functional constructs

• Companion objects
• Partial applied functions
• Currying
• Type inference and ascription
• First class functions
• High order functions

Socket

• Usage of 'ServerSocket' in Scala

SQL

• Data base connection in Scala

Concurrency

• Creating a 'Thread' in Scala
• Usage of thread pool based concurrency in Scala
• Object synchronization in Scala
• Usage of 'CountDownLatch' in Scala
• Usage of 'CyclicBarrier' is in Scala

Useful programs

• Verify all HTTP URLs of a markdown file
• Test for Anagram String in Scala
• Counter number of words per String in Scala
• Program to give runtime size of all primitive variables

Data structures

• A Stack implemented in Scala
• Reverse a word using a stack in Scala
• A Queue implemented in Scala
• A Circular Queue implemented in Scala

Finagle

• A simple HTTP service using Finagle

Spark

• Program to count 'words per statement'
• Program to count 'words per statement', arrived on network socket
• Program to show case RDD operations
• Program to show case DataFrame operations
• Program to show case DataSet operations
• Program to show various operations on Data retrieved from File
• Program to show Kryo based serialization
• Program to show hive connection