Android for Beginners : ReportCard Kotlin Class

ReportCard.kt

class ReportCard constructor(var name: String) {
    var englishGrade: Char? = null
    var mathGrade: String? = null
    var historyGrade: Int? = null
    var biologyGrade: Double? = null

    constructor(name: String, englishGrade: Char?, mathGrade: String?, historyGrade: Int?, biologyGrade: Double?) : this(name) {
        this.englishGrade = englishGrade
        this.mathGrade = mathGrade
        this.historyGrade = historyGrade
        this.biologyGrade = biologyGrade
    }

    override fun toString(): String {
        var reportMessage = "Name: $name;"
        englishGrade?.let { reportMessage += " English grade: $englishGrade;" }
        mathGrade?.let { reportMessage += " Math grade: $mathGrade;" }
        historyGrade?.let { reportMessage += " History grade: $historyGrade;" }
        biologyGrade?.let { reportMessage += " Biology grade: $biologyGrade;" }
        return reportMessage
    }
}

val reportCard = ReportCard("John Doe")
reportCard.englishGrade = 'A'
reportCard.mathGrade = "A-"
reportCard.historyGrade = 85
reportCard.biologyGrade = 90.5
println(reportCard) // Name: John Doe; English grade: A; Math grade: A-; History grade: 85; Biology grade: 90.5;

val reportCard2 = ReportCard("Second Doe", 'B', null, 70, 60.5)
println(reportCard2) // Name: Second Doe; English grade: B; History grade: 70; Biology grade: 60.5;

val students = arrayListOf<String>("Jane Doe", "Peter", "Jane")
val englishGrades = arrayListOf<Char>('B', 'C', 'D')
val mathGrades = arrayListOf<String?>("B+", "B", null)
val historyGrades = arrayListOf<Int?>(null, null, 80)
for ((index, student) in students.withIndex()) {
    val reportCard = ReportCard(student)
    reportCard.englishGrade = englishGrades.get(index)
    reportCard.mathGrade = mathGrades.get(index)
    reportCard.historyGrade = historyGrades.get(index)
    println(reportCard) 
}
// Name: Jane Doe; English grade: B; Math grade: B+;
// Name: Peter; English grade: C; Math grade: B;
// Name: Jane; English grade: D; History grade: 80;