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courseScala

Scala Basics


Goal: Understand expressions, variables, types, and type inference in Scala 2.

1. Expressions

An expression produces a value.

Scala
println(10 + 20)
println("Hello, Scala!")

Output


30
Hello, Scala!

Remember:Arithmetic operations, method calls, and string values can all be expressions.


2. val vs var

Use val for a value that cannot be reassigned. Use var when reassignment is required.

Scala
val name = "Deepak"
var age = 30
age = 31
println(name)
println(age)

Output

Deepak
31

val prevents reassignment of the variable; it does not automatically make every referenced object immutable.

Best practice: Prefer val unless you specifically need reassignment.


3. Type Inference

Scala can infer a variable's type from its initial value.

Scala
val name = "Deepak" // String
val age = 30        // Int
val salary = 50000.0 // Double

You can also declare the type explicitly:

val age: Int = 30

Both approaches are valid.

Remember: Scala is statically typed, even when you omit explicit type declarations.

4. Functions

A function accepts input and produces a result.

Scala
val add = (a: Int, b: Int) => a + b
println(add(10, 20))

Output

30

a: Int and b: Int are parameters.

=> separates the parameters from the function body.

a + b is the result.

5. Methods

Define a named method using def.

Scala
def multiply(a: Int, b: Int): Int = {  a * b}
println(multiply(4, 5))

Output

20

Key difference: A method is defined with def. A function is a value that can be stored in a variable, passed to another function, or returned.

Key Takeaways

​

  • Expressions produce values.

  • Use val by default and var when reassignment is necessary.

  • Scala infers types without sacrificing static type checking.

  • Use def to define methods.

  • Functions can be stored in values and passed around as data.