2.3

import java.io.File
import java.io.FileInputStream
import java.io.InputStream
import java.util.*

fun main(args: Array<String>) {
    val myMatrix1 = MyMatrix2("test.txt")
    myMatrix1.input()
    myMatrix1.print()
    val sum = myMatrix1.getSum()
    println("Сумма: $sum")
}


class MyMatrix2(
        private val fileName: String,
        n: Int = 2,
        m: Int = 2
) : MyMatrix1(n, m) {
    override fun input() {
        commonInput(FileInputStream(File(fileName))) {
            println("Была прочитана матрица из файла $fileName>")
        }
    }
}

open class MyMatrix1(
        val n: Int = 2,
        val m: Int = 2
) {
    private var data: Array<IntArray>? = null

    open fun input() {
        commonInput(System.`in`) {
            println("Введите ${n}x${m} элементов")
        }
    }

    protected fun commonInput(input: InputStream, body: () -> Unit) {
        val dataLocal = Array(n, { _ -> IntArray(m) })
        data = dataLocal

        val scanner = Scanner(input)
        body.invoke()

        for (row in 0 until n) {
            for (col in 0 until m)
                dataLocal[row][col] = scanner.nextInt()
        }
    }

    fun print() {
        val localData = data
        localData ?: return
        println("Матрица:")
        for (row in localData) {
            for (col in row)
                print("$col ")
            println()
        }
    }

    fun getSum(): Int = data?.sumBy { it.sum() } ?: 0
}

Test

fun main(args: Array<String>) {
    println("Я готов)")
}