Awesome

Android Interview Questions and Answers

Android Interview Questions and Answers - Your Cheat Sheet For Android Interview

Prepared and maintained by Amit Shekhar - Coder | Teacher | Mentor | Open Source | IIT 2010-14

About me

Hi, I am Amit Shekhar, Co-Founder @ Outcome School • IIT 2010-14 • I have taught and mentored many developers, and their efforts landed them high-paying tech jobs, helped many tech companies in solving their unique problems, and created many open-source libraries being used by top companies. I am passionate about sharing knowledge through open-source, blogs, and videos.

You can connect with me on:

• Twitter
• YouTube
• LinkedIn
• GitHub

Join Outcome School and get high paying tech job: Outcome School

Contents - Android Interview Questions

• Android Interview Questions and Answers Playlist
• Kotlin Coroutines
• Kotlin Flow API
• Kotlin
• Android
• Android Libraries
• Android Architecture
• Android System Design
• Android Unit Testing
• Android Tools And Technologies
• Java
• Jetpack Compose
• Other Topics
• Data Structures and Algorithms

Android Interview Questions and Answers Playlist

• Question: What is an inline function in Kotlin?
  • Answer: What is an inline function in Kotlin?
• Question: What is the advantage of using const in Kotlin?
  • Answer: What is the advantage of using const in Kotlin?
• Question: What is a reified keyword in Kotlin?
  • Answer: What is a reified keyword in Kotlin?
• Question: Suspending vs Blocking in Kotlin Coroutines
  • Answer: Suspending vs Blocking in Kotlin Coroutines
• Question: Launch vs Async in Kotlin Coroutines
  • Answer: Launch vs Async in Kotlin Coroutines
• Question: internal visibility modifier in Kotlin
  • Answer: internal visibility modifier in Kotlin
• Question: open keyword in Kotlin
  • Answer: open keyword in Kotlin
• Question: lateinit vs lazy in Kotlin
  • Answer: lateinit vs lazy in Kotlin
• Question: What is Multidex in Android?
  • Answer: What is Multidex in Android?
• Question: How does the Android Push Notification system work?
  • Answer: How does the Android Push Notification system work?
• Question: How does the Kotlin Multiplatform work?
  • Answer: How does the Kotlin Multiplatform work?
• Question: What is a ViewModel and how is it useful?
  • Answer: What is a ViewModel and how is it useful?
• Question: Is it possible to force the Garbage Collection in Android?
  • Answer: Is it possible to force Garbage Collection in Android?
• Question: What is a JvmStatic Annotation in Kotlin?
  • Answer: What is a JvmStatic Annotation in Kotlin?
• Question: init block in Kotlin
  • Answer: init block in Kotlin
• Question: JvmField Annotation in Kotlin
  • Answer: JvmField Annotation in Kotlin
• Question: singleTask launchMode in Android
  • Answer: singleTask launchMode in Android
• Question: Difference between == and === in Kotlin
  • Answer: Difference between == and === in Kotlin
• Question: JvmOverloads Annotation in Kotlin
  • Answer: JvmOverloads Annotation in Kotlin
• Question: Why is it recommended to use only the default constructor to create a Fragment?
  • Answer: Why is it recommended to use only the default constructor to create a Fragment?
• Question: Why do we need to call setContentView() in onCreate() of Activity class?
  • Answer: Why do we need to call setContentView() in onCreate() of Activity class?
• Question: When only onDestroy is called for an activity without onPause() and onStop()?
  • Answer: When only onDestroy is called for an activity without onPause() and onStop()?

Kotlin Coroutines

Topics you should know in Kotlin Coroutines for Android Interview:

• coroutines
• suspend
• launch, async-await, withContext
• dispatchers
• scope, context, job
• lifecycleScope, viewModelScope, GlobalScope
• suspendCoroutine, suspendCancellableCoroutine
• coroutineScope, supervisorScope

Learn the above-mentioned from the following links:

• Master Kotlin Coroutines
• Suspending vs Blocking in Kotlin Coroutines
• Launch vs Async in Kotlin Coroutines
• Dispatchers in Kotlin Coroutines
• coroutineScope vs supervisorScope
• suspend function in Kotlin Coroutines
• Kotlin withContext vs Async-await
• CoroutineContext in Kotlin
• Callback to Coroutines in Kotlin
• Retrofit with Kotlin Coroutines
• Parallel Multiple Network Calls Using Kotlin Coroutines
• Room Database with Kotlin Coroutines
• Unit Testing ViewModel with Kotlin Coroutines and LiveData

Kotlin Flow API

Topics you should know in Kotlin Flow API for Android Interview:

• Flow Builder, Operator, Collector
• flowOn, dispatchers
• Operators such as filter, map, zip, flatMapConcat, retry, debounce, distinctUntilChanged, flatMapLatest
• Terminal operators
• Cold Flow vs Hot Flow
• StateFlow, SharedFlow, callbackFlow, channelFlow

Learn the above-mentioned from the following links:

• Mastering Flow API in Kotlin
• Creating Flow Using Flow Builder in Kotlin
• Terminal Operators in Kotlin Flow
• Cold Flow vs Hot Flow
• StateFlow and SharedFlow
• Long-running tasks in parallel with Kotlin Flow
• Retry Operator in Kotlin Flow
• Retrofit with Kotlin Flow
• Room Database with Kotlin Flow
• Kotlin Flow Zip Operator for Parallel Multiple Network Calls
• Instant Search Using Kotlin Flow Operators
• callbackFlow - Callback to Flow API in Kotlin
• Exception Handling in Kotlin Flow
• Unit Testing ViewModel with Kotlin Flow and StateFlow

Kotlin

Android Interview Questions and Answers:

• What is the advantage of using const in Kotlin? - Video and Blog

• When to use lateinit keyword used in Kotlin? - Learn from here

• What is inline function in Kotlin? - Video and Blog

• What are companion objects in Kotlin? - Learn from here

• Extension functions - Learn from here

• What is a data class in Kotlin? - Learn from here

• Remove duplicates from an array in Kotlin - Learn from here

• What is a JvmStatic Annotation in Kotlin? - Video and Blog

• What is a JvmField Annotation in Kotlin? - Video and Blog

• What is a JvmOverloads Annotation in Kotlin? - Video and Blog

• noinline in Kotlin - Learn from here

• crossinline in Kotlin - Learn from here

• scope functions in Kotlin - Learn from here

• What is a reified keyword in Kotlin? - Learn from here

• lateinit vs lazy in Kotlin - Learn from here

• What is an init block in Kotlin? - Video and Blog

• Difference between == and === in Kotlin - Video and Blog

• Advantage of using const in Kotlin - Learn from here

• What are higher-order functions in Kotlin? - Learn from here: Higher-Order Functions and Lambdas in Kotlin

• What are Lambdas in Kotlin - Learn from here: Higher-Order Functions and Lambdas in Kotlin

• AssociateBy - List to Map in Kotlin - Learn from here

• Open keyword in Kotlin - Learn from here

• Companion object in Kotlin - Learn from here

• internal visibility modifier in Kotlin - Learn from here

• partition - filtering function in Kotlin - Learn from here

• Infix notation in Kotlin - Learn from here

• How does the Kotlin Multiplatform work? - Learn from here

• Suspending vs Blocking in Kotlin Coroutines - Learn from here

• String vs StringBuffer vs StringBuilder - Learn from here

• What is the difference between val and var? - Learn from here

• How to check if a lateinit variable has been initialized? - Learn from here

• How to do lazy initialization of variables in Kotlin? - Learn from here

• What are the visibility modifiers in Kotlin? - Learn from here

• What is the equivalent of Java static methods in Kotlin? - Learn from here

• How to create a Singleton class in Kotlin? - Learn from here

• What is the difference between open and public in Kotlin? - Learn from here

• Explain the use-case of let, run, with, also, apply in Kotlin. - Learn from here and here

• How to choose between apply and with? - Learn from here and here

• Difference between List and Array types in Kotlin - Learn from here

• What are Labels in Kotlin? - Learn from here

• What are Coroutines in Kotlin? - Learn from here

• What is Coroutine Scope? - Learn from here

• What is Coroutine Context? - Learn from here

• Launch vs Async in Kotlin Coroutines - Learn from here

• Thread.sleep() vs delay() in Kotlin - Learn from here

• Explain inline classes in Kotlin - Learn from here

• When to use Kotlin sealed classes? - Learn from here

• Tell about the Collections in Kotlin - Learn from here

• What does ?: do in Kotlin? (Elvis Operator) - Learn from here

Android

Android Interview Questions and Answers:

Base

• Why does an Android App lag? - Learn from here

• What is Context? How is it used? - Context In Android Application

• Tell all the Android application components. - Learn from here

• What is the project structure of an Android Application? - Learn from here

• What is AndroidManifest.xml? - Learn from here

• What is the Application class?

  • The Application class in Android is the base class within an Android app that contains all other components such as activities and services. The Application class, or any subclass of the Application class, is instantiated before any other class when the process for your application/package is created.

Activity and Fragment

• Why is it recommended to use only the default constructor to create a Fragment? - Learn from video and blog

• What is Activity and its lifecycle? - Learn from here

• What is the difference between onCreate() and onStart() - Learn from here

• When only onDestroy is called for an activity without onPause() and onStop()? - Learn from here

• Why do we need to call setContentView() in onCreate() of Activity class? - Learn from here

• What is onSaveInstanceState() and onRestoreInstanceState() in activity?

  • onSaveInstanceState() - This method is used to store data before pausing the activity.
  • onRestoreInstanceState() - This method is used to recover the saved state of an activity when the activity is recreated after destruction. So, the onRestoreInstanceState() receives the bundle that contains the instance state information.

• What is Fragment and its lifecycle? - Learn from here

• What are "launchMode"? - Learn from here and singleTask launchMode in Android

• What is the difference between a Fragment and an Activity? Explain the relationship between the two. - Learn from here

• When should you use a Fragment rather than an Activity?

  • When you have some UI components to be used across various activities
  • When multiple views can be displayed side by side just like ViewPager

• What is the difference between FragmentPagerAdapter vs FragmentStatePagerAdapter?

  • FragmentPagerAdapter: Each fragment visited by the user will be stored in the memory but the view will be destroyed. When the page is revisited, then the view will be created not the instance of the fragment.
  • FragmentStatePagerAdapter: Here, the fragment instance will be destroyed when it is not visible to the user, except the saved state of the fragment.

• What is the difference between adding/replacing fragment in backstack? - Learn from here

• How would you communicate between two Fragments?

• What is retained Fragment?

  • By default, Fragments are destroyed and recreated along with their parent Activities when a configuration change occurs. Calling setRetainInstance(true) allows us to bypass this destroy-and-recreate cycle, signaling the system to retain the current instance of the fragment when the activity is recreated.

• What is the purpose of addToBackStack() while commiting fragment transaction?

  • By calling addToBackStack(), the replace transaction is saved to the back stack so the user can reverse the transaction and bring back the previous fragment by pressing the Back button. For more Learn from here

Views and ViewGroups

• What is View in Android?

• Difference between View.GONE and View.INVISIBLE? - Learn from here

• Can you a create custom view? How?

• What are ViewGroups and how they are different from the Views?

  • View: View objects are the basic building blocks of User Interface(UI) elements in Android. View is a simple rectangle box which responds to the user’s actions. Examples are EditText, Button, CheckBox etc. View refers to the android.view.View class, which is the base class of all UI classes.
  • ViewGroup: ViewGroup is the invisible container. It holds View and ViewGroup. For example, LinearLayout is the ViewGroup that contains Button(View), and other Layouts also. ViewGroup is the base class for Layouts.

• What is a Canvas?

• What is a SurfaceView? - Learn from here

• Relative Layout vs Linear Layout.

• Tell about Constraint Layout

• Do you know what is the view tree? How can you optimize its depth? - Learn from here

Displaying Lists of Content

• What is the difference between ListView and RecyclerView? - Learn from here

• How does RecyclerView work internally?

• RecyclerView Optimization - Scrolling Performance Improvement - Learn from here

• Optimizing Nested RecyclerView - Learn from here

• How does RecyclerView improve performance over ListView?

• What are the components of a RecyclerView?

• Explain the role of RecyclerView.Adapter and RecyclerView.ViewHolder

• What is a LayoutManager in RecyclerView?

• How do you handle multiple view types in a single RecyclerView?

• What is DiffUtil and how does it improve RecyclerView performance?

• What is the purpose of RecyclerView.setHasFixedSize(true)?

• How do you update a specific item in RecyclerView?

• What is SnapHelper? - Learn from here: SnapHelper

Dialogs and Toasts

• What is Dialog in Android? - Learn from here

• What is Toast in Android? - Learn from here

• What the difference between Dialog and Dialog Fragment? - Learn from here

Intents and Broadcasting

• What is Intent? - Learn from here

• What is an Implicit Intent? - Learn from here

• What is an Explicit Intent? - Learn from here

• What is a BroadcastReceiver? - Learn from here

• What is a Sticky Intent?

  • Sticky Intents allows communication between a function and a service. sendStickyBroadcast() performs a sendBroadcast(Intent) known as sticky, i.e. the Intent you are sending stays around after the broadcast is complete, so that others can quickly retrieve that data through the return value of registerReceiver(BroadcastReceiver, IntentFilter). For example, if you take an intent for ACTION_BATTERY_CHANGED to get battery change events: When you call registerReceiver() for that action — even with a null BroadcastReceiver — you get the Intent that was last Broadcast for that action. Hence, you can use this to find the state of the battery without necessarily registering for all future state changes in the battery.

• Describe how broadcasts and intents work to be able to pass messages around your app? - Learn from here

• What is a PendingIntent?

  • If you want someone to perform any Intent operation at future point of time on behalf of you, then we will use Pending Intent.

• What are the different types of Broadcasts? - Learn from here

Services

• What is Service? - Learn from here

• Service vs IntentService - Learn from here

• What is a Foreground Service? - Learn from here

• What is a JobScheduler? - Learn from here

Inter-process Communication

• How can two distinct Android apps interact? - Learn from here

• Is it possible to run an Android app in multiple processes? How? - Learn from here

• What is AIDL? Enumerate the steps in creating a bounded service through AIDL. - Learn from here

• What can you use for background processing in Android? - Learn from here

• What is a ContentProvider and what is it typically used for? - Learn from here and here

Long-running Operations

• How to run parallel tasks and get a callback when all are complete? - Long-running tasks in parallel with Kotlin Flow

• What is ANR? How can the ANR be prevented? - Learn from here

• What is an AsyncTask(Deprecated in API level 30) ?

• What are the problems in AsyncTask?

• Daemon Threads vs. User Threads - Learn from here

• Explain Looper, Handler, and HandlerThread.

• Android Memory Leak and Garbage Collection

Working With Multimedia Content

• How do you handle bitmaps in Android as it takes too much memory? - Learn from here and here

• Tell about the Bitmap pool. - Learn from here

Data Saving

• Jetpack DataStore Preferences - Learn from here

• How to persist data in an Android app?

• What is ORM? How does it work?

• How would you preserve the Activity state during a screen rotation? - Learn from here

• What are different ways to store data in your Android app?

• Explain Scoped Storage in Android.

• How to encrypt data in Android?

• What is commit() and apply() in SharedPreferences?

  • commit() returns a boolean value of success or failure immediately by writing data synchronously.
  • apply() is asynchronous and it won't return any boolean response. If you have an apply() outstanding and you are performing commit(), then the commit() will be blocked until the apply() is not completed.

Look and Feel

• What is a Spannable?

• What is a SpannableString?

  • A SpannableString has immutable text, but its span information is mutable. Use a SpannableString when your text doesn't need to be changed but the styling does. Spans are ranges over the text that include styling information like color, heighliting, italics, links, etc

• What are the best practices for using text in Android?

• How to implement Dark mode in any application?

Memory Optimizations

• What is the onTrimMemory() method? - Learn from here

• How to identify and fix OutOfMemory issues?

• How do you find memory leaks in Android applications?

Battery Life Optimizations

• How to reduce battery usage in an android application?

• What is Doze? What about App Standby? - Learn from here

• What is overdraw? - Learn from here

Supporting Different Screen Sizes

• How do you support different types of resolutions? - Learn from here

Permissions

• What are the different protection levels in permission?

Native Programming

• What is the NDK and why is it useful? - Learn from here: Android NDK and RenderScript

• What is renderscript? - Learn from here: Android NDK and RenderScript

Android System Internal

• What is Android Runtime? - Android Runtime

• Dalvik, ART, JIT, and AOT in Android - Dalvik, ART, JIT, and AOT

• What are the differences between Dalvik and ART? - Difference between Dalvik and ART

• What is DEX? - Learn from here

• What is Multidex in Android? - Learn from here

• Can you manually call the Garbage collector? - Is it possible to force Garbage Collection in Android?

Android Jetpack

• What is Android Jetpack and why to use this?

• What is a ViewModel and how is it useful? Learn: What is a ViewModel and how is it useful?

• SharedViewModel in Android Learn: SharedViewModel in Android

• What are Android Architecture Components?

• What is LiveData in Android?

• How LiveData is different from ObservableField?

• What is the difference between setValue and postValue in LiveData?

• How to share ViewModel between Fragments in Android?

• Explain WorkManager and its use cases.

• How does ViewModel work internally?

Others

• What is the difference between Serializable and Parcelable? Which is the best approach in Android? - Learn from here

• Why Bundle class is used for data passing and why cannot we use simple Map data structure? - Learn from here

• How do you troubleshoot a crashing application? - Learn from here

• Explain the Android push notification system? Learn from here: How does the Android push notification system work?

• What is AAPT? - Learn from here

• FlatBuffers vs JSON.

• HashMap, ArrayMap and SparseArray - Learn from here

• What are Annotations? - Learn from here

• How to create custom Annotation? - Learn from here

• What is the support library? Why was it introduced?

• What is Android Data Binding?

Android Libraries

Android Interview Questions and Answers:

• Explain OkHttp Interceptor - Learn from here

• OkHttp - HTTP Caching - Learn from here

• Why do we use the Dependency Injection Framework like Dagger in Android?

• How does the Dagger work?

• How will you choose between Dagger 2 and Dagger-Hilt?

• What is a Component in Dagger?

• What is Module in Dagger?

• How does the custom scope work in Dagger?

• When to call dispose and clear on CompositeDisposable in RxJava? - Learn from here

• What is Multipart Request in Networking?

• What is Flow in Kotlin? - Learn from here

• App Startup Library - Learn from here

• Tell me something about RxJava.

• How will you handle error in RxJava?

• FlatMap Vs Map Operator - Learn from here

• When to use Create operator and when to use fromCallable operator of RxJava? - Learn from here: RxJava Create and fromCallable Operator

• When to use defer operator of RxJava? - Learn from here: RxJava Defer Operator

• How are Timer, Delay, and Interval operators used in RxJava? - Learn from here

• How to make two network calls in parallel using RxJava? - RxJava Zip Operator

• Tell the difference between Concat and Merge. - Learn from here and here

• Explain Subject in RxJava? - Learn from here

• What are the types of Observables in RxJava? - Learn from here: Types Of Observables In RxJava

• How to implement search feature using RxJava in your application? - Learn from here: Instant Search Using RxJava Operators

• Pagination In RecyclerView Using RxJava Operators - Learn from here

• How The Android Image Loading Library Glide and Fresco Works? - Learn from here, here and here

• Difference between Schedulers.io() and Schedulers.computation() in RxJava.

Android Architecture

Android Interview Questions and Answers:

• Describe the architecture of your last app.

• Describe MVVM. - MVVM Architecture

• MVC vs MVP vs MVVM architecture.

• Clean Architecture

• Software Architecture vs Software Design - Learn from here

Android System Design

Android Interview Questions and Answers:

• Design an Image Loading Library - Learn from here, here and here

• Design File Downloader Library - Learn from here

• Design WhatsApp

• Design Instagram Stories

• Design Networking Library

• Design Facebook Near-By Friends App

• Design Caching Library.

• Design problems based on location-based app

• How to build an offline-first app? Explain the architecture

• Design LRU Cache

• Design Analytics Library

• HTTP Request vs HTTP Long-Polling vs WebSockets - Learn from blog and Video - HTTP Request vs HTTP Long-Polling vs WebSocket vs Server-Sent Events

• How do Voice And Video Call Work? - Learn from here

• Design Uber App - Learn from here

• Database Normalization vs Denormalization - Database Normalization vs Denormalization

• Hash vs Encrypt vs Encode - Learn from here

Android Unit Testing

Android Interview Questions and Answers:

• Unit Testing ViewModel with Kotlin Coroutines and LiveData - Learn from here

• Unit Testing ViewModel with Kotlin Flow and StateFlow - Learn from here

• What is Espresso? - Learn from here

• What is Robolectric? - Learn from here

• What are the disadvantages of using Robolectric? - Learn from here

• What is UI-Automator? - Learn from here

• Explain the unit test. - Learn from here

• Explain instrumented test. - Learn from here

• Why Mockito is used? - Learn from here

• Describe code coverage.

Android Tools And Technologies

Android Interview Questions and Answers:

• What is ADB? - Learn from here

• What is the StrictMode? - Learn from here: StrictMode

• What is Lint? What is it used for?

• Git.

• Firebase. - Learn from here

• How to measure method execution time in Android?

• Can you access your database of SQLite Database for debugging? - Learn from here

• What are things that we need to take care while using Proguard?

• How to use Android Studio Memory Profiler?

• What is Gradle?

• APK Size Reduction.

• How can you speed up the Gradle build?

• About gradle build system.

• About multiple apk for android application.

• What is ProGuard used for? - Learn from here

• What is obfuscation? What is it used for? What about minification?

• How to change some parameters in an app without app update?

• What is Write-Ahead Logging (WAL) and why it is used internally in databases? - Learn from here

Java

Android Interview Questions and Answers:

OOP

• Explain OOP Concepts.

• Differences between abstract classes and interfaces?

  • An abstract class, is a class that contains both concrete and abstract methods (methods without implementations). An abstract method must be implemented by the abstract class sub-classes. Abstract classes cannot be instantiated and need to be extended to be used.
  • An interface is like a blueprint/contract of a class (or it may be thought of as a class with methods, but without their implementation). It contains empty methods that represent, what all of its subclasses should have in common. The subclasses provide the implementation for each of these methods. Interfaces are implemented.

• Difference between method overloading and overriding.

• What are the access modifiers you know? What does each one do?

  • There are four access modifiers in Java language (from strictest to the most lenient):
    1. private variables, methods, constructors or inner classes are only visible to its' containing class and its' methods. This modifier is most commonly used, for example, to allow variable access only through getters and setters or to hide underlying implementation of classes that should not be used by user and therefore maintain encapsulation. Singleton constructor is also marked private to avoid unwanted instantiation from outside.
    2. Default (no keyword is used) this modifier can be applied to classes, variables, constructors and methods and allows access from classes and methods inside the same package.
    3. protected can be used on variables, methods and constructors therefore allowing access only to subclasses and classes that are inside the same package as protected members' class.
    4. public modifier is widely-used on classes, variables, constructors and methods to grant access from any class and method anywhere. It should not be used everywhere as it implies that data marked with public is not sensitive and can not be used to harm the program.

• Can an Interface implement another Interface?

  • Yes, an interface can implement another interface (and more than one), but it needs to use extends, rather than implements keyword. And while you can not remove methods from parent interface, you can add new ones freely to your sub-interface.

• What is Polymorphism? What about Inheritance?

Collections and Generics

• Arrays Vs ArrayLists - Learn from here

• HashSet Vs TreeSet - Learn from here

• HashMap Vs Set - Learn from here

• Explain Generics in Java?

Objects and Primitives

• How is String class implemented? Why was it made immutable?

  • There is no primitive variant of String class in Java language - all strings are just wrappers around underlying array of characters, which is declared final. This means that, once a String object is instantiated, it cannot be changed through normal tools of the language (Reflection still can mess things up horribly, because in Java no object is truly immutable). This is why String variables in classes are the first candidates to be used, when you want to override hashCode() and equals() of your class - you can be sure, that all their required contracts will be satisfied.

    Note: The String class is immutable, so that once it is created a String object cannot be changed. The String class has a number of methods, some of which will be discussed below, that appear to modify strings. Since strings are immutable, what these methods really do is create and return a new string that contains the result of the operation. (Official Java Documentation)

    This class is also unique in a sense, that, when you create an instance like this:

    String helloWorld = "Hello, World!";
    

    "Hello, World!" is called a literal and compiler creates a String object with its' value. So

    String capital = "Hello, World!".toUpperCase();
    

    is a valid statement, that, firstly, will create an object with literal value "Hello, World!" and then will create and return another object with value "HELLO, WORLD!"

  • String was made immutable to prevent malicious manipulation of data, when, for example, user login or other sensitive data is being send to a server.

• What does it means to say that a String is immutable?

  • It means that once created, String object's char[] (its' containing value) is declared final and, therefore, it can not be changed during runtime.

• Can you list 8 primitive types in java?

  • byte
  • short
  • int
  • long
  • float
  • double
  • char
  • boolean

• What is the difference between an Integer and int?

  • int is a primitive data type (with boolean, byte, char, short, long, float and double), while Integer (with Boolean, Byte, Character, Short,Long, Float and Double) is a wrapper class that encapsulates primitive data type, while providing useful methods to perform different tasks with it.

• Do objects get passed by reference or value in Java? Elaborate on that.

Java Memory Model and Garbage Collector

• What is garbage collector? How does it work?
  • All objects are allocated on the heap area managed by the JVM. As long as an object is being referenced, the JVM considers it alive. Once an object is no longer referenced and therefore is not reachable by the application code, the garbage collector removes it and reclaims the unused memory.

Concurrency

• What does the keyword synchronized mean?

• What is a ThreadPoolExecutor? - ThreadPoolExecutor in Android

• What is volatile modifier?

• Object Level Lock vs Class Level Lock in Java - Learn from here

• Concurrency vs Parallelism - Learn from here

• The classes in the atomic package expose a common set of methods: get, set,, lazyset, compareAndSet, and weakCompareAndSet. Please describe them.

Exceptions

• How does the try{}, catch{}, finally works?

• What is the difference between a Checked Exception and an Un-Checked Exception?

Others

• Shallow vs. Deep Copy in Java - Learn from here

• Explain Serialization and Deserialization - Learn from here

• What is serialization? How do you implement it?

• What is transient modifier?

• What are anonymous classes?

• What is the difference between using == and .equals on an object?

• What is the hashCode() and equals() used for?

• When would you make an object value final?

• What are these final, finally and finalize keywords?

• What is the difference between "throw" and "throws" keyword in Java?

  • throws is just used to indicated which exception is to be thrown. But the throw keyword is used to throw some exception from any static block or any method.

• What does the static word mean in Java?

  • In case of static variable it means that this variable (its' value or the object it references) spans across all instances of enclosing class (changing it in one instance affects all others), while in case of static methods it means that these methods can be invoked without an instance of their enclosing class. It is useful, for example, when you create util classes that need not be instantiated every time you want to use them.

• Can a static method be overridden in Java?

  • While child class can override a static method with another static method with the same signature (return type can be down-casted), it is not truly overridden - it becomes "hidden", but both methods can still be accessed under right circumstances (see question about overloading/overriding above).

• When is a static block run?

  • Code inside static block is executed only once: the first time you make an object of that class or the first time you access a static member of that class (even if you never make an object of that class).

• Explain Reflection in Java - Learn from here

• What is Dependency Injection?

• Difference between StringBuffer and StringBuilder? - Learn from here

• What is the difference between fail-fast and fail-safe iterators in Java?

• Monitor and Synchronization

Jetpack Compose

Topics you should know in Jetpack Compose for Android Interview:

• Compose
• State: remember, rememberSaveable, MutableState
• Recomposition
• State hoisting
• Side-effects
• Modifier
• Theme
• Layout, List
• Gestures, Animation
• CompositionLocal

Learn the above-mentioned from the following links:

• Getting Started with Compose
• Thinking in Compose
• State
• remember vs rememberSaveable
• Lifecycle
• Modifiers
• Side-effects
• Phases
• Semantics
• CompositionLocal
• Can we use traditional Android Views and Compose together?

Questions

• Jetpack Compose vs Android View System

• Explain the concept of declarative UI in Jetpack Compose.

• Declarative UI vs Imperative UI

• What are Composable functions?

• What is Recomposition?

• What is State in Compose?

• How does state management work in Jetpack Compose?

• Stateful composable vs Stateless composable

• What are the side effects?

• Difference between LaunchedEffect and DisposableEffect.

• What is rememberCoroutineScope and its use cases?

• How to observe Flows, and LiveData states in Compose UI?

• How can we handle asynchronous operations in Jetpack Compose?

• How can we convert a non-compose state into a Compose state?

• Explain derivedStateOf.

• Explain rememberUpdatedState.

• Difference between remember and rememberSaveable.

• Explain the Lifecycle of a Composable in Jetpack Compose.

• How do you handle lifecycle events in Compose functions?

• What are the best practices for performance optimization in Jetpack Compose?

• Can we use both Jetpack Compose and Android View in a Single App?

• What is State Hoisting?

• Explain CompositionLocal

• Explain Jetpack Compose Phases.

• What is the role of the Modifier in Jetpack Compose?

• What are Semantics?

• How can you handle user input and events in Jetpack Compose?

• How do you handle navigation in Jetpack Compose?

• How do you handle orientation changes in Jetpack Compose?

• Explain the concept of unidirectional data flow in Jetpack Compose.

• How to create Custom Layouts in Compose?

Other Topics

Android Interview Questions and Answers:

• Describe SQLite.

• Have you used Room-Database?

• Can we identify the users who have uninstalled our application?

• Android Development Best Practices. - Learn from here: Android Development Best Practices

• React Native vs Flutter - Learn from here: React Native vs Flutter

• What are the metrics that you should measure continuously while android application development? - Learn from here: Android App Performance Metrics

• How to avoid API keys from check-in into VCS?

• How does the Kotlin Multiplatform work? - Blog

• How to use Memory Heap Dumps data?

• How to implement Dark Theme in your app?

• How to secure the API keys used in an Android App?

• Tell something about memory usage in Android.

• Explain Annotation processing.

• How does the Android Push Notification system work? Learn from here: How does the Android Push Notification system work?

• How to show local Notification at an exact time?

Data Structures and Algorithms

• Android Developer should know these Data Structures for Next Interview - Check here

High-quality videos to prepare for Android Interview - Amit Shekhar YouTube Channel

High-quality blogs to prepare for Android Interview - Check here - Outcome School Blog

Found this project useful :heart:

• Support by clicking the :star: button on the upper right of this page. :v:

You can connect with me on:

• Twitter
• YouTube
• LinkedIn
• GitHub

License

   Copyright (C) 2024 Amit Shekhar

   Licensed under the Apache License, Version 2.0 (the "License");
   you may not use this file except in compliance with the License.
   You may obtain a copy of the License at

       http://www.apache.org/licenses/LICENSE-2.0

   Unless required by applicable law or agreed to in writing, software
   distributed under the License is distributed on an "AS IS" BASIS,
   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   See the License for the specific language governing permissions and
   limitations under the License.