An Example Kotlin Program

                fun main() {
                    val results = mutableListOf<Result>()

                    while (true) {
                        print("Name: ")
                        val name = readln()
                        if (name.isBlank()) break

                        var mark: Int?
                        do {
                            print("Mark: ")
                            mark = readln().toIntOrNull()
                        } while (mark == null)

                        results.add(Result(name, mark))
                    }

                    println("Class Results")
                    println("-".repeat(32))

                    results.sortByDescending { it.mark }

                    results.forEachIndexed { i, result ->
                        println("${i+1}. $result")
                    }

                    val total = results.sumOf { it.mark }
                    val average = total.toDouble() / results.size

                    println("-".repeat(32))
                    println("Average Mark %.1f".format(average))
                }

                class Result (
                    val name: String,
                    val mark: Int
                ) {
                    fun grade(): String = when (mark) {
                        in 0..24 -> "Not Achieved"
                        in 25..49 -> "Achieved"
                        in 50..74 -> "Merit"
                        in 75..100 -> "Excellence"
                        else -> "unknown"
                    }

                    override fun toString(): String {
                        var info = name.padEnd(15)
                        info += mark.toString().padStart(3)
                        info += "  " + grade()
                        return info
                    }
                }
            

Program Output

This program shows off some of the neat, concise Kotlin syntax: data collections, classes, forEach, when, String templates, null safety, etc.

Here is an example run for the program:

                $ java -classpath kotlin-stdlib.jar MainKt

                Name: Jimmy Smith
                Mark: 13

                Name: Shelly Gnome
                Mark: 100

                Name: Tane Jones
                Mark: 78

                Name: Dave Turnip
                Mark: 32

                Name: Karen Lentil
                Mark: ⏎
                Mark: ⏎
                Mark: 59

                Name: Kate Williams
                Mark: 85

                Name: Tim Gorilla
                Mark: 8

                Name: ⏎

                Class Results
                -----------------------------------
                1. Shelly Gnome   100  Excellence
                2. Kate Williams   85  Excellence
                3. Tane Jones      78  Excellence
                4. Katen Lentil    59  Merit
                5. Dave Turnip     32  Achieved
                6. Jimmy Smith     13  Not Achieved
                7. Tim Gorilla      8  Not Achieved
                -----------------------------------
                Average Mark 53.6

                $ Process finished with exit code 0