devDeejay

// Creating a Kotlin Class
class KotlinClass(var id: Long, var name: String, var url: String, var mbid: String) {
    fun print() {
        println("Printing through the function defined in the class")
    }
}

// This is our main function - which is pretty similar to the main method of Java
fun main(args: Array<String>) {
    // Creating a variable of type KotlinClass (defined above) and assigning null and adding a '?' to tell that this variable can be null

devDeejay

// Just imagine a closed existing class which you cannot modify, but you want to add some additional functionality to it
class KotlinClass(var id: Long, var name: String, var url: String, var mbid: String) {
    fun print() {
        println("Printing through the function defined in the class")
    }
}

fun main(args: Array<String>) {

devDeejay

        Button button = null; // Just creating a null button
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                Snackbar snackbar = Snackbar.make(findViewById(android.R.id.content), "Welcome To Main Activity", Snackbar.LENGTH_LONG);
                snackbar.show();
            }
        });

devDeejay

button.setOnClickListener {MainActivity.showSnackBarMessage("Kotlin is awesome")}

devDeejay

    // Creating a function to add two Int in Kotlin :

    fun add(number1: Int, number2: Int): Int {
        return number1 + number2
    }

    // The above function can be simplified and can be written as 

    fun add(number1: Int, number2: Int): Int = number1 + number2

devDeejay

    // Create a function and pass default values
    fun addNumbers(num1: Int = 0, num2: Int = 0, num3: Int = 0): Int = num1 + num2 + num3

    // These all are valid calls
    addNumbers()
    addNumbers(1)
    addNumbers(1,2)
    addNumbers(1,2,3)

devDeejay

    // Create a function and pass default values
    fun addNumbers(num1: Int = 0, num2: Int = 0, num3: Int = 0): Int = num1 + num2 + num3

    // These all are valid calls
    addNumbers()
    addNumbers(1)
    addNumbers(1,2)
    addNumbers(1,2,3)

    // And if you just want to pass second and third argument, you can do like this  :

devDeejay

class ActivityObserver : LifecycleObserver {
    private val TAG = this.javaClass.simpleName

    // OnCreate Event
    @OnLifecycleEvent(Lifecycle.Event.ON_CREATE)
    public fun onCreateEvent() {
        Log.d(TAG, "Observer OnCreate")
    }
    
    // OnPause Event 

devDeejay

class ProcessImageActivity : AppCompatActivity() {
    // Declaring viewModel variable
    private lateinit var viewModel : ProcessImageViewModel
    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_process_image)
        
        // Attaching the view model
        viewModel = ViewModelProviders.of(this).get(ProcessImageViewModel::class.java)
        

devDeejay

class ProcessImageViewModel : ViewModel() {
  
    private val TAG = this.javaClass.simpleName
  
    override fun onCleared() {
        super.onCleared()
        // This function gets called before view model gets destroyed
    }

    fun uploadImageAndRecognize(imageBitmap : Bitmap) {