Variables, Types and String Templates

val vs var

val site = "groovygrails.in"  // read-only, prefer always
var visits = 0               // mutable when truly needed
visits += 1

Type Inference

The compiler infers types, but they are still static: val n = 42 is an Int forever. Declare explicitly at API boundaries: fun total(): Int.

Number and Other Types

• Int, Long, Double, Float - no primitives vs wrappers split in code.
• Boolean, Char, String - familiar semantics.
• Arrays, Ranges - 1..10 and arrayOf(1, 2, 3).

String Templates

val lang = "Kotlin"
println("I love $lang")              // simple name
println("Next year: ${2026 + 1}")    // any expression

Multiline Strings

val json = """
  { "site": "groovygrails.in" }
""".trimIndent()

Key Points

• Default to val; var only with a reason.
• Templates replace string concatenation and formatters.
• Types are inferred but never dynamic.