What is Case Class in Scala?

In Scala, case classes are used to shape the immutable data and use pattern matching to decompose it. It is similar to regular classes and the parameter used in Case Class is immutable and public.

When we define a Class as a Case Class, then we don’t need to use the new keyword to create a new instance.

case class Person(name: String, relation: String)

What is Case Object in Scala?

In Scala, a Case object is also an object that is defined with a “case” modifier.

val krish = Person("krish", "joshi")

Case Class Benefits

The following are some of the benefits of Scala Case Class.

  • Scala Compiler adds toString, hashCode, and equals methods by default to avoid manual writing.
  • Scala Compiler adds copy method by default.
  • Scala Case classes are easily used in Pattern Matching.
  • In Scala, the Case objects & class are by default Serializable
  • We can define Algebraic data types by using Case Classes.

Case Class without the new keyword

The following examples show that we can see that Case Class is created without the “new” keyword, It is allowed to use the “new” keyword, but not recommended.

case class Person(name: String, relation: String) val krish = Person("krish", "joshi")



Case Class without mutator methods

In Scala, the default constructor parameters of Case Class are Val and hence for each parameter, the accessor method is created but not the mutator methods.

krish.name val res8: String = krish krish.name="joan" error: reassignment to val



Case Class unapply methods

In Scala, The unapply method is created automatically in Vase Class.

krish match { case Person(n, r) => println(n, r) }



Case Class copy method

The copy method is used in cloning the object so that any change in fields can be performed.

case class WorldCupteam(name: String, lastWorldSeriesWin: Int) val team2019 = WorldCupteam("England", 2019) val team2015 = team2019.copy(lastWorldSeriesWin = 2015)



Case Class equals and hashCode methods

By using equals and hashCode methods we can easily use our objects in collections like sets and maps.

val John = Person("John", "Wick") krish == John



Case Class equals toString methods

toString is a default method that is used in debugging a code. If we just write down the variable name it will show it's class and variable name.

krish val res1: Person = Person(krish,joshi)



How to check Code Generated by Case Class?

We can see the code that Scala case classes generate. To do that, first, compile a simple case class, then disassemble the resulting .class files with javap.

Create a scala file with the name caseclasscode.scala and put below statement.

case class caseclasscode(var name: String, var age: Int)

Compile the code from the command prompt. Please use the below command to compile.

scalac caseclasscode.scala

scalac creates two JVM class files, caseclasscode.class and caseclasscode $.class. Disassemble caseclasscode.class with this command.

Use javap to see the public signature of the class

javap caseclasscode



Click Here To Download Code File.