----------------------------------------------------------------------------------------
    MainActivity..kt
----------------------------------------------------------------------------------------
class MainActivity : AppCompatActivity() {
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //텍스트뷰 초기화
        var textView : TextView = findViewById(R.id.textView);

        var a = 10
        do{
            textView.append("do-while문 실행 \n")
        }while(a > 20)

        var i = 0
        do {
            textView.append("i is $i \n")
            i++
        } while (i < 5)

    }
}

----------------------------------------------------------------------------------------
    activity_main.xml
----------------------------------------------------------------------------------------
<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <TextView
        android:id="@+id/textView"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="30sp"
        android:textStyle="bold"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>