App is now fully converted to Kotlin

app/src/main/java/com/denizd/substitutionplan/SubstDatabase.kt

@@ -0,0 +1,30 @@
+package com.denizd.substitutionplan
+
+import android.content.Context
+import androidx.room.Database
+import androidx.room.Room
+import androidx.room.RoomDatabase
+
+@Database(entities = [Subst::class], version = 3, exportSchema = false)
+public abstract class SubstDatabase : RoomDatabase() {
+
+    abstract fun substDao(): SubstDao
+
+    companion object {
+
+        private var instance: SubstDatabase? = null
+
+        fun getInstance(context: Context): SubstDatabase? {
+            if (instance == null) {
+                synchronized (SubstDatabase::class) {
+                    instance = Room.databaseBuilder(context.applicationContext,
+                            SubstDatabase::class.java,
+                            "subst_database")
+                            .fallbackToDestructiveMigration()
+                            .build()
+                }
+            }
+            return instance
+        }
+    }
+}