How to initialize database in kotlin in function onCreate? - database

Question

I have MainActivity.kt and DBHelper.kt files in the same package com.example.shooter. In MainActivity.kt file, I try to initialize database of class DBHelper. I have written following line of code in onCreate() function in MainActivity:
DBHelper db = new DBHelper(applicationContext)
db is highlighted in red and says 'Unresolved reference'. Class DBHelper has onCreate method in it:
class DBHelper(context: Context):SQLiteOpenHelper(context, DATABASE_NAME,
null, DATABASE_VER
) {
companion object {
private val DATABASE_VER = 2
private val DATABASE_NAME = "EDMTDB.db"
//Table
private val TABLE_NAME = "LoginPassword"
private val COL_ID = "Id"
private val COL_LOGIN = "Login"
private val COL_PASSWORD = "Password"
}
// create table
override fun onCreate(db: SQLiteDatabase?) {
val CREATE_TABLE_QUERY = ("CREATE TABLE $TABLE_NAME " +
"($COL_ID INTEGER PRIMARY KEY AUTOINCREMENT, " +
"$COL_LOGIN TEXT NOT NULL, " +
"$COL_PASSWORD TEXT NOT NULL)")
db!!.execSQL(CREATE_TABLE_QUERY)
}
...(ommited some code)...
My question is, how to initialize the database in onCreate method in MainActivity.kt?