Some useful Scala examples
Language constructs
Hello World
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
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
SQL
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
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