External MySQL database in Kotlin

I'm making a Kotlin application which should have an external MySQL database. How can I set it up to get desired results?

The application should get a result from External MySQL database as a string. I already tried to use this link but It seems that there is something wrong.

I use this code:

class DBConnection {
    internal var conn: Connection? = null
    internal var username = "some username" 
    internal var password = "some password" 

    fun executeMySQLQuery() {
        var stmt: Statement? = null
        var resultset: ResultSet? = null
        try {
            stmt = conn!!.createStatement()
            resultset = stmt!!.executeQuery("SHOW DATABASES;")
            if (stmt.execute("SHOW DATABASES;")) {
                resultset = stmt.resultSet
            }
            while (resultset!!.next()) {
                println(resultset.getString("Database"))
            }
        } catch (ex: SQLException) {
            // handle any errors
            ex.printStackTrace()
        } finally {
            // release resources
            if (resultset != null) {
                try {
                    resultset.close()
                } catch (sqlEx: SQLException) {
                }
                resultset = null
            }
            if (stmt != null) {
                try {
                    stmt.close()
                } catch (sqlEx: SQLException) {
                }
                stmt = null
            }
            if (conn != null) {
                try {
                    conn!!.close()
                } catch (sqlEx: SQLException) {
                }
                conn = null
            }
        }
    }

    fun getConnection() {
        val connectionProps = Properties()
        connectionProps.put("user", username)
        connectionProps.put("password", password)
        try {
            Class.forName("com.mysql.jdbc.Driver").newInstance()
            conn = DriverManager.getConnection(
                "jdbc:" + "mysql" + "://" +
                        "remotemysql.com" +
                        ":" + "3306" + "/" +
                        "",
                connectionProps)
        } catch (ex: SQLException) {
            // handle any errors
            ex.printStackTrace()
        } catch (ex: Exception) {
            // handle any errors
            ex.printStackTrace()
        }
    }
}

And in a main file I use this:

val submit: Button = findViewById(R.id.submitBtn)
submit.setOnClickListener{
                val dbConnection: DBConnection
                dbConnection = DBConnection()
                dbConnection.getConnection()
                dbConnection.executeMySQLQuery()

        }

For now I just need to get a result from the database. When I used the mentioned code I got this error

E/AndroidRuntime: FATAL EXCEPTION: main
    Process: sk.letsdream, PID: 18521
    kotlin.KotlinNullPointerException
        at sk.letsdream.dbMethods.DBConnection.executeMySQLQuery(DBConnection.kt:19)
        at sk.letsdream.DochadzkaActivity$onCreate$2.onClick(DochadzkaActivity.kt:86)
        at android.view.View.performClick(View.java:7125)
        at android.view.View.performClickInternal(View.java:7102)
        at android.view.View.access$3400(View.java:801)
        at android.view.View$PerformClick.run(View.java:27301)
        at android.os.Handler.handleCallback(Handler.java:883)
        at android.os.Handler.dispatchMessage(Handler.java:100)
        at android.os.Looper.loop(Looper.java:214)
        at android.app.ActivityThread.main(ActivityThread.java:7319)
        at java.lang.reflect.Method.invoke(Native Method)
        at com.android.internal.os.RuntimeInit$MethodAndArgsCaller.run(RuntimeInit.java:492)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:934)

EDIT: After adding mysql-connector-java-8.0.16 it gives me an error that min. SDK should be 26. But after changing SDK to 26 it gives me this type error:

java.lang.BootstrapMethodError: Exception from call site #39 bootstrap method
        at com.mysql.cj.jdbc.AbandonedConnectionCleanupThread.<clinit>(AbandonedConnectionCleanupThread.java:58)

Where 58. line is:

Class.forName("com.mysql.jdbc.Driver").newInstance()

When we had older version of mysql connector mysql-connector-java-5.1.47 it threw this error:

com.mysql.jdbc.exceptions.jdbc4.MySQLNonTransientConnectionException: Could not create connection to database server.

on this line of code:

var conn = DriverManager.getConnection("jdbc:mysql://remotemysql.com:3306/My_DB_Name", connectionProps)

from External MySQL database in Kotlin