Simple example difference between multithreaded vs non-multithreaded code

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    tools:context=".MainActivity">

    <TextClock
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="24sp"
        android:format24Hour="HH:mm:ss"
        android:format12Hour="hh:mm:ss a"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="24dp" />

    <Button
        android:id="@+id/nonMultiThreadButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="24dp"
        android:text="Heavy Task Non Multithread" />


    <Button
        android:id="@+id/multiThreadButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="Heavy Task Multithread" />

    <Button
        android:id="@+id/coroutineButton"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:text="Heavy Task Coroutine" />

</LinearLayout>

MainActivity.kt

package id.thony.examplethread

import android.os.Bundle
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import kotlinx.android.synthetic.main.activity_main.*
import kotlinx.coroutines.*

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

        nonMultiThreadButton.setOnClickListener { heavyTaskNonMultiThread() }
        multiThreadButton.setOnClickListener { heavyTaskMultiThread() }
        coroutineButton.setOnClickListener {
            GlobalScope.launch {
                heavyTaskCoroutine()
            }
        }
    }

    private fun heavyTaskNonMultiThread() {
        Thread.sleep(5000)
        Toast.makeText(this, "Heavy task complete!", Toast.LENGTH_SHORT).show()
    }

    private fun heavyTaskMultiThread() {
        Thread {
            Thread.sleep(5000)
            this.runOnUiThread {
                Toast.makeText(this, "Heavy task complete!", Toast.LENGTH_SHORT).show()
            }
        }.start()
    }

    private suspend fun heavyTaskCoroutine() {
        delay(5000)
        withContext(Dispatchers.Main) {
            Toast.makeText(this@MainActivity, "Heavy task complete!", Toast.LENGTH_SHORT).show()
        }
    }
}