Android Interview Questions 2022

JAVA

• Why String is mutable?
• String str1 = 10

                String str2 = 20

        str1 == str2 is this true?

• What String Pool in java?
• Difference of StringBuffer vs String?
• Difference of StringBuilder vs StringBuffer?
• What is HashMap and purpose?
• Difference of HashMap vs HashTable?
• Difference of HashMap vs HashSet?
• What is array vs list?
• What is abstract class in java?
• What is collections in java?
• What is flatmap?
• What is array vs arraylist?
• What is Interface in Java?
• What is polymorphism ?
• What is singleton class?
• The following variable stored in which memory?

                String str = new String()  - memory?

        String str = “test”;

        String str1 = “test”;            - memory?

• Difference of == and equals() method in java?
• Program: Segregate the 01 int array [0100110100] to [0000001111]
• Write a program for fibno series?
• Write a program for palindrom? Eg: 121, madam
• Write a program input [12345678] to output [76812345]
• Write a program for vowels from given string?
• Write a program: Get duplicate data count from given int array [122333344455]

KOTLIN

• Singleton class in kotlin?
• What is scope functions in kotlin?
• str?.let() - is this working?
• Which operator used for null check? !!
• What is companion object?
• Difference of companion object and @JvmStatic keyword in kotlin?
• What is @JvmStatic, @JvmOverload, @JvmField, @JvmClass
• What is lateinit vs lazy?
• What is data class?
• Data class is open class?
• What are the classes in kotlin?
• Every class is in kotlin can inheritable?
• Difference of sealed class and enum class?
• What are the null safe operators in kotlin?
• What is difference between java and kotlin?
• Advantages of kotlin in android?
• Which version officially announce for android app development?
• What is Notnull variable in kotlin?
• What is primary constructor in kotlin?
• How to communicate between primary and secondary constructor?
• Difference between primary and secondary constructors in kotlin?
• What are the scopes in kotlin?
• Difference of GlobalScope and CoroutineScope and ViewModeScope?
• What is launch, async?
• What is the difference of launch, async and withContent() in kotlin?
• Write foreach in kotlin?
• Difference of == and === in kotlin?

ANDROID

• What is aar and apk?
• What is activity?
• What is service?
• What is stickyBroadcast?
• What is pending Intent?
• What is broadcast receiver?
• What is content provider?
• What is coroutine?
• What is suspend method and purpose?
• What are the lifecycle methods in Activity?
• What is different between onCreate() and onRestart()?
• What are the lifecycle methods in Fragment?

onattache, oncreate, oncreateview, onviewcreated, onviewstaterestored, onstart, onresume, onpause, onstop, onsaveinstancestate, ondestroyview, ondestroy, ondetach

• What is the difference between add/replace in a fragment?
• What are the lifecycle methods in Service?

oncreate(), onstartcommand(), onbind(), onrebind(), onunbind(), ondestroy()

• How to stop the service?

stopService(Intent) and stopSelf() methods used to stop the service

• Difference between Service and Intent Service?
• What is JobSchedule and purpose?
• What is Foreground service and purpose?
• What is MVVM?
• Explain the Difference of MVP and MVVM?
• How to share the data between activities?
• What is difference of list view and recyclerView?
• Advantages of recycler View?
• What are the permission states is in android?

- Normal permission

                -internet, bluetooth, networkstate, networkchange, wifi change

        - Danger permission

                - camera, microphone, sms, call, storage, location, gps, contact

        - Signature permission

                - write setting, write voice mail, read voice mail

        - Special permission

                - system_alarm_window

• What are the main components in android?
• What is the broadcast receiver and purpose?
• What is a content provider?
• How to share the data between the two services?
• Broadcast receiver will be register and deregister in which activity lifecycle?
• onStart() and onStop()
• What is databinding?
• Difference of viewBinding and databinding in android?
• What is fragmentContainerView?
• Advantages of recyclerView in android?
• Difference between listview and recyclerview?
• What is local broadcast manager?
• What is serializable and parcelable?
• What is Thread, Handler and asynctask?
• What is the difference of WorkManager vs CoroutineWorker?
• What is synchronous?
• Difference of Sqlite and Room?
• What is @Volatile?
• What is flow in android kotlin?
• What is paging and purpose?
• What is jetpack component in android?
• Purpose of Faculty ViewModel in android?
• What is lifecycle observer?
• What is live data in android?
• Difference of live data and state flow?
• What is rxjava?
• What is jetpack compose?
• Difference types of dispatchers?
• Purpose of onrestore instance state in fragment lifecycle?
• What is hilt in android?
• What is solid principles?
• What is launch mode in android?
• Difference of SingleTop and SingleInstance in android?
• How to handle the data in android?
• What is stickyIntent?
• What is sharedviewmodel in android?
• What is observable?
• What is the difference between constraint layout and coordinate layout ?
• How does the FCM push notification work ?
• What is Intent and its types ?
• Is storing values in shared preferences temporarily or permanent ?
• For e.g. : If there is a splash screen, login screen and home page. And after closing the app and opening again how to go home page from splash page directly Explain ?
• What are the components in Dagger2 ?
• What is the use of Inject and Provided in Dagger2 ?
• What is the architecture modal you are using in android and explain how it works?
• In Sqlite when does the OnUpdate call actually ? And how does it know when to call OnUpdate ?
• How to pass data from fragment to its base activity ?
• What is a singleton and its use ?
• What is the use of view holder? And why do we go for it ?
• Have you used any of the latest component in android jetpack ?
• What is Appcompat and Contextcompat ? Why do we \use them ? What is the difference between the two ?
• In what format the data is being stored in shared preferences ?
• What are the issues faced in 8.0 in some devices for push notifications ? Ans: We need to use Notification Channel for that.
• How to do face recognition ?
• How to pass objects between two activities ?
• What is a static block ?
• What are all the dependency you have used ?
• What is a design pattern ?
• What is gradle and maven ? What language is used ?
• If task is running in doInBackground in Async Task and if screen is rotated to Async Task calls again . Then what happens to previous running task ? will it get stopped ? Crash ? How to avoid this scenario.
• If battery low alert shows what happens to the current running app ? Will it get stopped or destroyed ?
• How many builds can you generate ? Ans : Debug, Release and Custom.