Android-Interview-Questions ===========================

Collaboration Rules

Make sure your question is new and unique - not just rephrasing a previously existing question. If possible, include a link to the solution/topic. Questions should be fairly straightforward and completely technical (no "how many golf balls are in America" questions.) If there is a new topic that you think should be included, then include it!

Topics:

• General Developer Questions
• Core Java
• Core Android
• Android Design and XML
• Android Networking
• Databases

General Developer Questions

• How familiar you are with the Android and Google Guidelines?
• Describe Test-Driven Development. [[info]](http://en.wikipedia.org/wiki/Test-driven\_development)
• Explain unit tests versus functional tests.
• Describe Scrum and Kanban.
• What project management tools have you used?
• How do you ensure that you are working efficiently?
• Do you have basic familiarity with working on the command line i.e. Gradle, Ant, or the Java Compiler?

Core Java

Object-Oriented Programming

• What are the main 3 Object Oriented Programing (OOP) concepts?
• Explain object serialization and how to implement it in Java.
• Explain anonymous classes. [[info]](http://docs.oracle.com/javase/tutorial/java/javaOO/anonymousclasses.html)
• Describe the differences between abstract classes and interfaces. [[info]](http://www.javaworld.com/article/2077421/learn-java/abstract-classes-vs-interfaces.html)
• Explain what a Singleton class is and how to create one in Java [[info]](http://www.javaworld.com/article/2073352/core-java/simply-singleton.html)
• Why should the equals() and hashCode() methods often be overridden together? [[info]](http://stackoverflow.com/questions/2265503/why-do-i-need-to-override-the-equals-and-hashcode-methods-in-java/2265637#2265637)
• How do you properly override the equals() method? For example, what considerations should be taken when checking for equality? [[info]](http://www.geeksforgeeks.org/overriding-equals-method-in-java/)
• Difference between final, finally and finalize?
• In Java, does the finally block gets executed if we insert a return statement inside the try block of a try-catch-finally? [[info]](https://stackoverflow.com/a/65049/497132)
• Explain method overloading & overriding.
• What is memory leak and how does Java handle it? [[info]](https://stackify.com/memory-leaks-java/)

Data Structures

• What are the use cases and differences of arrays and ArrayLists?
• What are the use cases and differences of a HashSet and a TreeSet? [[info]](https://stackoverflow.com/a/4464394/497132)

Build Tools

• Have you used any Ant, Maven, Gradle features for your project?

Programming Paradigms

• Explain event-driven programming in Java [[info]](http://en.wikibooks.org/wiki/Java\Programming/Event\Handling)
• What is Java's Garbage Collection and how does it help you as a developer?
• How can you typecast in Java? [[info]](http://www.studytonight.com/java/type-casting-in-java)
• Explain Java's try-catch-finally paradigm [[info]](http://www.studytonight.com/java/try-and-catch-block.php)

Core Android

• How does the Android notification system work?
• How can two distinct Android apps interact? (several answers)
• Describe Activities. [[info]](http://developer.android.com/reference/android/app/Activity.html)
• What are the four states of the Activity Lifecycle? [[active/running, paused, stopped, destroyed]](https://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle)
• What are the seven callback methods of an Activity used to perform operations when the Activity transitions between states? [[onCreate(), onStart(), onResume(), onPause(), onStop(), onRestart(), onDestroy()]](https://developer.android.com/reference/android/app/Activity.html#ActivityLifecycle)
• What is the difference between a fragment and an activity? Explain the relationship between the two. [[info]](https://stackoverflow.com/a/45252253/497132)
• What is the difference between Serializable and Parcelable? Which is the best approach in Android? [[info]](https://stackoverflow.com/a/50114007/497132)
• What are "launch modes"? [[info]](https://android.jlelse.eu/android-activity-launch-mode-e0df1aa72242)
• What are Intents? [[info]](http://developer.android.com/guide/components/intents-filters.html)
• What is an Implicit Intent? [[info]](https://developer.android.com/guide/components/intents-filters.html#ExampleSend)
• What is an Explicit Intent? [[info]](https://developer.android.com/guide/components/intents-filters.html#ExampleExplicit)
• Describe three common use cases for using an Intent.
• What is a Service? [[info]](http://developer.android.com/guide/components/services.html)
• What is a ContentProvider and what is it typically used for? [[info]](http://developer.android.com/guide/topics/providers/content-providers.html)
• What is a Fragment? [[info]](http://developer.android.com/guide/components/fragments.html)
• What is ADB?
• What is ANR?
• What is AndroidManifest.xml used for? Give examples of what kind of data you would add to it. [[info]](http://developer.android.com/guide/topics/manifest/manifest-intro.html)
• Describe how broadcasts and intents work to be able to pass messages around your app.[[info]](http://www.techotopia.com/index.php/Android\Broadcast\Intents\and\Broadcast\_Receivers)
• What is the Dalvik Virtual Machine?
• What are different ways to store data in your Android app? [[info]](https://developer.android.com/guide/topics/data/data-storage.html)
• Android appplication components [[info]](http://www.tutorialspoint.com/android/android\application\components.htm)
• What is the relationship between the life cycle of an AsyncTask and an Activity? What problems can this result in? How can these problems be avoided?[[info]](https://li2.gitbooks.io/android-programming-journey/content/Background_Tasks/what-is-the-relationship-between-the-life-cycle-of-an-asynctask-and-an-activity.html)
• What is the difference between Service and IntentService? How is each used? [[info]](https://stackoverflow.com/a/15772151/497132)
• What is a Sticky Intent? [[info]](https://stackoverflow.com/a/26038985/497132)
• What is AIDL? [[info]](https://developer.android.com/guide/components/aidl.html)
• What is dependency injection?
• What are the different protection levels in permission? [[info]](https://developer.android.com/guide/topics/manifest/permission-element.html)
• How would you preserve Activity state during a screen rotation?

Android Design and XML

• Explain the differences and similarities of Relative Layout and Linear Layout.
• Explain the differences and similarities of List Views and Grid Views.
• Describe how to implement XML namespaces.
• Explain how to present different styles/drawables for a button depending

• for layout\width and layout\height, what's the difference between match\parent and wrap\content?
• How do you implement Google's new Material Design in an Android application? [[info]](https://developer.android.com/training/material/get-started.html)
• Difference between View.GONE and View.INVISIBLE? [[info]](https://stackoverflow.com/a/11556629/497132)

Android Networking

• Have you use an HTTP Library, which, why, did you like it?
• Describe how REST APIs work.
• What are some typical methods of HTTP request/responses? [[GET, POST, PUT, PATCH, DELETE, UPDATE]](http://www.restapitutorial.com/lessons/httpmethods.html)

Databases

• Why does Android use SQLite?
• What libraries have you used for interacting with databases and why did you choose them?
• What are contract classes? [[info]](https://stackoverflow.com/a/36265603/497132)
• How do you use the BaseColumns interface to describe your data schema? [[info]](https://stackoverflow.com/a/7900591/497132)