Java Coding Interview Questions

In this article, We will discuss about Java Coding Interview Questions and their Answers. Moreover, we will try to provide multiple approaches to solve a coding problem. Additionally, related concepts to a particular coding problem will also be discussed. Our primary focus of this article is to provide all kinds of Java Coding Interview Questions with their Answers. However, for theoretical questions & answers of Java Interview, kindly visit our another article ‘[Java Interview Questions](https://javatechonline.com/java-interview-questions/)‘.

**Table of Contents (Click on links below to navigate) [**[**hide**](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#)**]**

* [1 How to iterate and modify value in Java 8 in a Map?](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#How_to_iterate_and_modify_value_in_Java_8_in_a_Map)
* [1.1 Output](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#Output)
* [2 How to print keys & values of a Map in Java 8 ?](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#How_to_print_keys_values_of_a_Map_in_Java_8)
* [3 How many ways are there to print keys & values of a Map ?](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#How_many_ways_are_there_to_print_keys_values_of_a_Map)
* [4 How to convert String to Date Object in Java 8 ?](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#How_to_convert_String_to_Date_Object_in_Java_8)
* [4.1 Output](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#Output-2)
* [5 How many ways are there to initialize a Set ?](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#How_many_ways_are_there_to_initialize_a_Set)
* [6 How to create various collections using Factory Method of Java 9 ?](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#How_to_create_various_collections_using_Factory_Method_of_Java_9)
* [7 How to retrieve values from Set in Java 8 ?](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#How_to_retrieve_values_from_Set_in_Java_8)
* [8 How to iterate a Map containing a List of String in Java 8 ?](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#How_to_iterate_a_Map_containing_a_List_of_String_in_Java_8)
* [8.1 Output ](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#Output-3)
* [9 How to count occurrences of each character of a String in Java 8?](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#How_to_count_occurrences_of_each_character_of_a_String_in_Java_8)
* [9.1 Output](https://javatechonline.com/java-coding-interview-questions/?utm_source=rss&#Output-4)

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Marielle Rippin

1595098800

Android Interview Questions – Get ready for your next interview

Android – one of the hottest technologies, which is having a bright future. Get ready to crack your next interview with the following android interview questions. These interview questions start with basic and cover deep concepts along with advanced topics.

Android Interview Questions for Freshers

1. What is Android?

Android is an open-source mobile operating system that is based on the modified versions of Linux kernel. Though it was mainly designed for smartphones, now it is being used for Tablets, Televisions, Smartwatches, and other Android wearables.

2. Who is the inventor of Android Technology?

The inventors of Android Technology are- Andry Rubin, Nick Sears, and Rich Miner.

3. What is the latest version of Android?

The latest version of Android is Android 10.0, known as Android Q. The upcoming major Android release is Android 11, which is the 18th version of Android. [Note: Keep checking the versions, it is as of June 2020.]

4. How many Android versions can you recall right now?

Till now, there are 17 versions of Android, which have their names in alphabetical order. The 18th version of Android is also going to come later this year. The versions of Android are here:

Android 1.0 – Its release is 23 September 2008.
Android 1.1 – Its release date is 9 February 2009.
Android 1.5 – Its name is Cupcake, Released on 27 April 2009.
Android 1.6 – Its name is Donut, Released on 15 September 2009.
Android 2.0 – Its name is Eclair, Released on 26 October 2009
Android 2.2 – Its name is Froyo, Released on 20 May 2010.
Android 2.3 – Its name is Gingerbread, Released on 06 December 2010.
Android 3.0 – Its name is Honeycomb, Released on 22 February 2011.
Android 4.0 – Its name is Ice Cream Sandwich, Released on 18 October 2011.
Android 4.1 – Its name is Jelly Bean, Released on 9 July 2012.
Android 4.4 – Its name is KitKat, Released on 31 October 2013.
Android 5.0 – Its name is Lollipop, Released on 12 November 2014.
Android 6.0 – Its name is Marshmallow, Released on 5 October 2015.
Android 7.0 – Its name is Nougat, Released on 22 August 2016.
Android 8.0 – Its name is Oreo, Released on 21 August 2017.
Android 9.0 – Its name is Pie, Released on 6 August 2018.
Android 10.0 – Its name is Android Q, Released on 3 September 2019.
Android 11.0 – As of now, it is Android 11.

5. Explain the Android Architecture with its components.

This is a popular android developer interview question

Android Architecture consists of 5 components that are-

a. Linux Kernel: It is the foundation of the Android Architecture that resides at the lowest level. It provides the level of abstraction for hardware devices and upper layer components. Linux Kernel also provides various important hardware drivers that act as software interfaces for hardwares like camera, bluetooth, etc.

b. Native Libraries: These are the libraries for Android that are written in C/C++. These libraries are useful to build many core services like ART and HAL. It provides support for core features.

c. Android Runtime: It is an Android Runtime Environment. Android Operating System uses it during the execution of the app. It performs the translation of the application bytecode into the native instructions. The runtime environment of the device then executes these native instructions.

d. Application Framework: Application Framework provides many java classes and interfaces for app development. And it also provides various high-level services. This complete Application framework makes use of Java.

e. Applications: This is the topmost layer of Android Architecture. It provides applications for the end-user, so they can use the android device and compute the tasks.

6. What are the services that the Application framework provides?

The Android application framework has the following key services-

a. Activity Manager: It uses testing and debugging methods.

b. Content provider: It provides the data from application to other layers.

c. Resource Manager: This provides users access to resources.

d. Notification Manager: This gives notification to the users regarding actions taking place in the background.

e. View System: It is the base class for widgets, and it is also responsible for event handling.

7. What are the important features of Linux Kernel?

The important features of the Linux Kernel are as follows:

a. Power Management: Linux Kernel does power management to enhance and improve the battery life of the device.

b. Memory Management: It is useful for the maximum utilization of the available memory of the device.

c. Device Management: It includes managing all the hardware device drivers. It maximizes the utilization of the available resources.

d. Security: It ensures that no application has any such permission that it affects any other application in order to maintain security.

e. Multi-tasking: Multi-tasking provides the users the ease of doing multiple tasks at the same time.

8. What are the building blocks of an Android Application?

This is a popular android interview question for freshers.

The main components of any Android application are- Activity, Services, Content Provider, and Broadcast Receiver. You can understand them as follows:

a. Activity- It is a class that acts as the entry point representing a single screen to the user. It is like a window to show the user interface.

b. Services- Services are the longest-running component that runs in the background.

c. Content Provider- The content provider is an essential component that allows apps to share data between themselves.

d. Broadcast receivers- Broadcast receiver is another most crucial application component. It helps the apps to receive and respond to broadcast messages from the system or some other application.

9. What are the important components of Android Application?

The Components of Android application are listed below:

Widgets
Intents
Views
Notification
Fragments
Layout XML files
Resources

10. What are the widgets?

Widgets are the variations of Broadcast receivers. They are an important part of home screen customization. They often display some data and also allow users to perform actions on them. Mostly they display the app icon on the screen.

11. Can you name some types of widgets?

Mentioned below are the types of widgets-

a. Informative Widgets: These widgets show some important information. Like, the clock widget or a weather widget.

b. Collective Widgets: They are the collection of some types of elements. For example, a music widget that lets us change, skip, or forward the song.

c. Control Widgets: These widgets help us control the actions within the application through it. Like an email widget that helps check the recent mails.

d. Hybrid Widgets: Hybrid widgets are those that consist of at least two or more types of widgets.

12. What are Intents?

Intents are an important part of Android Applications. They enable communication between components of the same application as well as separate applications. The Intent signals the Android system about a certain event that has occurred.

13. Explain the types of intents briefly?

Intent is of three types that are-

a. Implicit Intents: Implicit intents are those in which there is no description of the component name but only the action.

b. Explicit Intents: In explicit intents, the target component is present by declaring the name of the component.

c. Pending Intents: These are those intents that act as a shield over the Intent objects. It covers the intent objects and grants permission to the external app components to access them.

14. What is a View?

A view is an important building block that helps in designing the user interface of the application. It can be a rectangular box or a circular shape, for example, Text View, Edit Text, Buttons, etc. Views occupy a certain area of the screen, and it is also responsible for event handling. A view is the superclass of all the graphical user interface components.

15. What do you understand by View Group?

It is the subclass of the ViewClass. It gives an invisible container to hold layouts or views. You can understand view groups as special views that are capable of holding other views, that are Child View.

16. What do you understand about Shared Preferences?

It is a simple mechanism for data storage in Android. In this, there is no need to create files, and using APIs, it stores the data in XML files. It stores the data in the pair of key-values. SharedPreferences class lets the user save the values and retrieve them when required. Using SharedPreferences we can save primitive data like- boolean, float, integer, string and long.

17. What is a Notification?

A notification is just like a message that shows up outside the Application UI to provide reminders to the users. They remind the user about a message received, or some other timely information from the app.

18. Give names of Notification types.

There are three types of notifications namely-

a. Toast Notification- This notification is the one that fades away sometime after it pops up.

b. Status Notification- This notification stays till the user takes some action on it.

c. Dialog Notification- This notification is the result of an Active Activity.

19. What are fragments?

A fragment is a part of the complete user interface. These are present in Activity, and an activity can have one or more fragments at the same time. We can reuse a fragment in multiple activities as well.

20. What are the types of fragments?

There are three types of fragments that are: Single Fragment, List Fragment, Fragment Transactions.

Single Transactions can only show a single view for the user.
List Fragments have a special list view feature that provides a list from which the user can select one.
Fragment Transactions are helpful for the transition between one fragment to the other.

Frequently asked Android Interview Questions and Answers

21. What are Layout XML files?

Layout XML files contain the structure for the user interface of the application. The XML file also contains various different layouts and views, and they also specify various GUI components that are there in Activity or fragments.

22. What are Resources in Android Application?

The resources in Android Apps defines images, texts, strings, colors, etc. Everything in resources directory is referenced in the source code of the app so that we can use them.

23. Can you develop Android Apps with languages other than Java? If so, name some.

Yes, there are many languages that we can work with, for the development of Android Applications. To name some, I would say Java, Python, C, C++, Kotlin, C#, Corona/LUA.

24. What are the states of the Activity Lifecycle?

Activity lifecycle has the following four stages-

a. Running State: As soon as the activity starts, it is the first state.

b. Paused State: When some other activity starts without closing the previous one, the running activity turns into the Paused state.

c. Resume State: When the activity opens again after being in pause state, it comes into the Resume State.

d. Stopped State: When the user closes the application or stops using it, the activity goes to the Stopped state.

25. What are some methods of Activity?

The methods of Activity are as follows:

onCreate()
onStart()
onPause()
onRestart()
onResume()
onStop()
onDestroy()

26. How can you launch an activity in Android?

We launch an activity using Intents. For this we need to use intent as follows:

ntent intent_name= new Intent(this, Activity_name.class);
startActivity(intent_name);

27. What is the service lifecycle?

There are two states of a service that are-

a. Started State: This is when the service starts its execution. A Services come in start state only through the startService() method.

b. Bounded State: A service is in the bounded state when it calls the method bindService().

28. What are some methods of Services?

The methods of service are as follows-

onStartCommand()
onBind()
onCreate()
onUnbind()
onDestroy()
onRebind()

29. What are the types of Broadcast?

Broadcasts are of two types that are-

a. Ordered Broadcast: Ordered broadcasts are Synchronous and work in a proper order. It decides the order by using the priority assigned to the broadcasts.

b. Normal Broadcast: These are asynchronous and unordered. They are more efficient as they run unorderly and all at once. But, they lack full utilization of the results.

30. What are useful impotent folders in Android?

The impotent folders in an Android application are-

build.xml- It is responsible for the build of Android applications.
bin/ – The bin folder works as a staging area to wrap the files packages into the APK.
src/ – The src is a folder where all the source files of the project are present.
res/ – The res is the resource folder that stores values of the resources that are used in the application. These resources can be colors, styles, strings, dimensions, etc.
assets/ – It provides a facility to include files like text, XML, fonts, music, and video in the Android application.

31. What are the important files for Android Application when working on Android Studio?

This is an important android studio interview question

There are following three files that we need to work on for an application to work-

a. The AndroidManifest.xml file: It has all the information about the application.

b. The MainActivity.java file: It is the app file that actually gets converted to the dalvik executable and runs the application. It is written in java.

c. The Activity_main.xml file: It is the layout file that is available in the res/layout directory. It is another mostly used file while developing the application.

32. Which database do you use for Android Application development?

The database that we use for Android Applications is SQLite. It is because SQLite is lightweight and specially developed for Android Apps. SQLite works the same way as SQL using the same commands.

33. Tell us some features of Android OS.

The best features of Android include-

Multi-tasking
Support for a great range of languages
Support for split-screen
High connectivity with 5G support
Motion Control

34. Why did you learn Android development?

Learning Android Studio is a good idea because of the following-

It has a low application development cost.
It is an open-source platform.
It has multi-platform support as well as Multi-carrier support.
It is open for customizations.
Android is a largely used operating system throughout the world.

35. What are the different ways of storage supported in Android?

The various storage ways supported in Android are as follows:

Shared Preference
Internal Storage
External Storage
SQLite Databases
Network Connection

36. What are layouts?

Layout is nothing but arrangements of elements on the device screen. These elements can be images, tests, videos, anything. They basically define the structure of the Android user interface to make it user friendly.

37. How many layout types are there?

The type of layouts used in Android Apps are as follows:

Linear Layout
Relative Layout
Constraint Layout
Table Layout
Frame Layout
Absolute Layout
Scrollview layout

38. What is an APK?

An APK stands for Android Package that is a file format of Android Applications. Android OS uses this package for the distribution and installation of the Android Application.

39. What is an Android Manifest file?

The manifest file describes all the essential information about the project application for build tools, Android operating system, and google play. This file is a must for every Android project that we develop, and it is present in the root of the project source set.

#android tutorials #android basic interview questions #android basic questions #android developer interview questions #android interview question and answer #android interview questions #android interview questions for experienced #android interview questions for fresher

Samanta Moore

1621137960

Guidelines for Java Code Reviews

Get a jump-start on your next code review session with this list.

Having another pair of eyes scan your code is always useful and helps you spot mistakes before you break production. You need not be an expert to review someone’s code. Some experience with the programming language and a review checklist should help you get started. We’ve put together a list of things you should keep in mind when you’re reviewing Java code. Read on!

1. Follow Java Code Conventions

2. Replace Imperative Code With Lambdas and Streams

3. Beware of the `NullPointerException`

4. Directly Assigning References From Client Code to a Field

5. Handle Exceptions With Care

…

#java #code quality #java tutorial #code analysis #code reviews #code review tips #code analysis tools #java tutorial for beginners #java code review

Tyrique Littel

1600135200

How to Install OpenJDK 11 on CentOS 8

What is OpenJDK?

OpenJDk or Open Java Development Kit is a free, open-source framework of the Java Platform, Standard Edition (or Java SE). It contains the virtual machine, the Java Class Library, and the Java compiler. The difference between the Oracle OpenJDK and Oracle JDK is that OpenJDK is a source code reference point for the open-source model. Simultaneously, the Oracle JDK is a continuation or advanced model of the OpenJDK, which is not open source and requires a license to use.

In this article, we will be installing OpenJDK on Centos 8.

#tutorials #alternatives #centos #centos 8 #configuration #dnf #frameworks #java #java development kit #java ee #java environment variables #java framework #java jdk #java jre #java platform #java sdk #java se #jdk #jre #open java development kit #open source #openjdk #openjdk 11 #openjdk 8 #openjdk runtime environment

Were Joyce

1620815880

How to Prepare for a Coding Interview in 8 Weeks

As of this writing, the market is tough. We’ve been hit hard with a deadly

pandemic that left thousands of people unemployed. It’s layoffs everywhere and the companies are being conservative when it comes to

hiring.

Companies are not willing to hire people with no experience or people who they’ve to train.

Your first job in tech is the toughest, you’re competing

with virtually every new college grad and anyone who completed a boot

camp. I know it can be hard to even land an interview, for someone to

give you a chance to talk and demonstrate you could be valuable

employee.

Now, the chance of you getting an interview totally depends on how your resume compares to the job description. The more relevant it is to the

skills required, the better your chances of getting an interview.

To build your resume, I’d recommend https://thetechresume.com. It’s a nice read to follow the principles when it comes to building a tech resume.

Over the past few months, I’ve been collecting resources like videos,

websites, and taking notes to prepare for coding interviews.

In that process, I made an 8 weeks study guide curated of important data

structure resources to prepare for tech interviews and honestly this

study guide was helpful to me to know what to study every day and in

following a routine for my job search.

Why 8 weeks?

If you’re serious about preparing for a tech interview then 8 weeks is the

minimum to be given to prepare thoroughly for a tech interview. I know

there are few who would cram up pools of content in a week or two. But, I

believe that is not a realistic or sensible approach.

Tech interviews can be intense and most companies expect you to solve problems or go through a data structure topic in detail.

Now, My study guide with resources will eat up the entire blog space. So,

Instead of straight-up dumping down the content all together, I racked

my brains on how to deliver the content in the most effective way

possible to ensure the habit of consistency and dedication stays intact

during the interview preparation process.

In this blog post, I would give you what to cover each week. If you’re

interested to know what resources to refer to when covering each topic then I’d recommend subscribing to the newsletter https://thedailycoding.com in which you’ll receive one email daily about the concept and the resources to practice.

If you believe you can find resources to relevant topics on your own then

here’s how you should plan to cover each topic every week.

#coding-interviews #software-development #job-interview #job-search #coding #latest-tech-stories #coding-interview-tips #coding-job-interview-advice

Java Coding Interview Questions

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