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What are Sealed classes?

Sealed classes and interfaces represent restricted class hierarchies that provide more control over inheritance. All direct subclasses of a sealed class are known at compile time. No other subclasses may appear after a module with the sealed class is compiled.

So, what gives it more control on handling UI state?

As we can see that all subclasses of a sealed class is known at compile time it gives us the ability to use it inside when block and the compiler is able to warn us if any branch is not handled, in exactly the same way that it does for enumerations.

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import android.content.ContentResolver
import android.content.Context
import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.graphics.Matrix
import android.media.MediaMetadataRetriever
import android.net.Uri
import android.os.Build
import android.provider.MediaStore

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import android.graphics.Rect
import android.view.View
import androidx.recyclerview.widget.RecyclerView
import androidx.recyclerview.widget.RecyclerView.ItemDecoration


class GridSpacingItemDecoration(
    private val spanCount: Int,

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GSON

TypeAdapter

We can create custom type adapters for dirty JSON files. Suppose we have a JSON text like below:

{
  "id": 2,
  "name": "Alif Hasnain",
  "age": {
    "age": 24,
    "mature": true

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import android.Manifest;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.IntentSender;
import android.content.pm.PackageManager;
import android.os.Looper;

import androidx.core.app.ActivityCompat;
import androidx.lifecycle.Lifecycle;
import androidx.lifecycle.LifecycleObserver;

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Single, Maybe and Completable in brief

Comprehensive Guide by MindOrks Here

Various use cases for Observable

Observable's subscribe to an observer. Observer emits the state of the Observable.

For Observable creation. See this

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import android.content.Context
import android.net.ConnectivityManager
import android.net.Network
import android.net.NetworkCapabilities
import android.net.NetworkRequest
import android.os.Build
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData

/**

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Remote

Add new remote

git remote add <origin_name> <url_of_the_remote_repo>

Update existing remote

git remote set-url <origin> <url_of_the_remote_repo>

To see remotes names

git remote

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Instantiate a mock object (Without Annotation)

Mockito.mock(ClassName.class);

Instantiate a mock object (With Annotation)

@RunWith(MockitoJUnitRunner.class)
public class MyTestClassTest {

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class Event<out R>(private val data: R) {

    var hasEventBeenHandled = false
    private set

    val content: R?
        get() = if (!hasEventBeenHandled) {
            hasEventBeenHandled = true
            data
        } else {