Blog Archives

00: 15+ Java multi-threading interview Q&As

Even the experienced Java developers dread Java multithreading interview questions & coding exercises. Interviewers love to drill you on multithreading as it can reveal a lot about your capabilities.

Q1. What is a thread?
A1. It is a thread of execution in a program.

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00: 17 beginner Java interview questions and answers

These 17 beginner Java interview questions & answers are not only for the entry level job interviews, but also get a good grasp of the beginner level Java concepts.

Q1. Why use Java?
A1. Java is a very popular language as per the TIOBE index.

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00: Q1 – Q6 Hadoop based Big Data architecture & basics interview Q&As

There are a number of technologies to ingest & run analytical queries over Big Data (i.e. large volume of data). Big Data is used in Business Intelligence (i.e. BI) reporting, Data Science, Machine Learning, and Artificial Intelligence (i.e. AI). Processing a large volume of data will be intensive on disk I/O,

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00: ⏯ MySQL database beginner video tutorial

Step by step MySQL video tutorial to get started with MySQL database. Any decent self-taught projects require a database to store & retrieve data.

Related Links

1. Getting started with MySQL database beginner tutorial.

SQL Interview Q&As

1. 14 FAQ SQL Interview Questions &

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001A: 7+ Java architectural patterns interview Q&As

One of the very frequently asked open-ended interview questions is – Can you describe the high-level architecture of the recent application you had worked on from 10,000 feet? ⏯ Java high-level architecture & Integration Styles

You will be asked to 1) draw a diagram on a white board and 2) follow up questions based on your answer.

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01: 12 Web basics every Java web developer must know

Q1. HTTP is a stateless protocol, so how do you maintain state? How do you store user data between requests?
A1. This is a commonly asked interview question. The “http protocol is a stateless request/response based protocol”. You can retain the state information between different page requests as follows:

HTTP Session.

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01: 6 must know Java Web Services Interview Q&As

As an enterprise Java developer, you will be spending more time integrating systems via Java web services & messaging. Java Web Services interview questions are must know for the Java developers.

Q1. What are the different styles of Web Services used for application integration?

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01: Spring DI & IoC interview Q&As

Video: Spring DIP, DI, and IoC. This extends 13 Spring interview questions & answers.

Q1. What do you understand by the terms Dependency Inversion Principle (DIP), Dependency Injection (DI) and Inversion of Control (IoC) container?

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01a: ⏯ Spring MVC beginner video tutorial step by step

Related Links

1. Spring MVC beginner tutorial step by step.

Extends Video Tutorials

1. ⏯ Java Web App with Tomcat & Maven beginner video tutorial.

2. ⏯ Running Tomcat inside Eclipse beginner video tutorial.

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02: 10 Java String class interview Q&As

Java Collection interview questions and answers and Java String class interview questions and answers are must know for any Java developer as these two APIs are the most frequently used in your Java application code. You can’t write any decent Java application without these 2 APIs.


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02: Java Compile-time Vs Run-time Interview Q&As

During development and design, one needs to think in terms of compile-time, run-time, and build-time. It will also help you understand the fundamentals better. These are beginner to intermediate level questions.


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02: Java Generics in no time “? extends” & “? super” explained with a diagram

Generics in Java can be be a bit tricky to get your head around. Hope the explanation below enhances your understanding of generics. This complements 5 Java generics interview Q&As with examples.

Plain old List, List <Object>, and List<?>

The plain old List: is a heterogeneous mixture or a mixed bag that contains elements of all types,

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02: What is wrong with this code? Heap Vs Stack, Thread safety & Synchronized

This post covers must know Java Multithreading basics – Heap Vs Stack, Thread-safety & Synchronization. When you have a multithreaded Java application, you need to code in a thread-safe manner. Java interviewers may ask you to detect thread-safety issues as discussed in “What is wrong with this code?

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03: ♦ Java autoboxing & unboxing benefits & caveats interview Q&As

Q1. What do you understand by the terms “autoboxing” and “autounboxing” in Java?
A1. Java automatically converts a primitive type like “int” into corresponding wrapper object class Integer. This is known as the autoboxing. When it converts a wrapper object class Integer back to its primitive type “int”,

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04: 5 FAQs on transforming your thinking from OOP to FP

Functional programming is prevalent in data engineering (i.e. Spark programming, etc) roles. A must know for Big Data Engineers and Analysts.

One needs to get used to the transformation from imperative programming to functional programming. You like it or not, you will be using functional programming in Java,

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06: HashMap & HashSet and how do they internally work? What is a hashing function?

HashMap & HashSet are not only one of the frequently used data structures, but also one of the popular interview topics.

Q1. How does a HashMap store data?
A1. As key/value pairs. You can store and retrieve values with the keys.

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06: ⏯ Tell us about yourself? video

Java developers often need to tackle open ended questions like Tell us about yourself?, Describe a project you are most proud of?, Give us an instance where you fixed an issue that is hard to reproduce?,

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07. ⏯ Spring DI with Maven beginner video tutorial

Related Links

1. Spring DIP, DI & IoC in detail interview Q&As.

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1 – 4 real life examples of SAR technique

The open-ended questions give you a great opportunity to promote your strengths and accomplishments. SAR (Situation-Action-Result) technique examples.

Example 1: Tuning performance

Situation: Performance problem where the application server had to be restarted every second day.

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13: 5 Ways to debug Java thread-safety issues

Interviewers often judge your experience with debugging skills. For example, debugging jar hell issues, debugging SSL issues, debugging hibernate issues, debugging transaction management issues, etc. All these are covered in detail under the key areas “Key Area – Debug xxxx

How will you debug thread-safety issues in Java?

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14+ SQL interview Q&As

SQL interview Questions & Answers is a must for any developer as all non-trivial applications need to talk to a database with CRUD operations. Q3 – Q15 are very popular with the interviewers. If you want to quickly practice your SQL skills try DB Fiddle or install MySQL locally as shown in the ⏯ MySQL database beginner video tutorial.

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15 Apache Spark best practices & performance tuning interview FAQs

There are so many different ways to solve the big data problems at hand in Spark, but some approaches can impact on performance, and lead to performance and memory issues. Here are some best practices to keep in mind when writing Spark jobs.

General Best Practices

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15 Spring Boot interview Q&As

15 Spring boot interview questions & answers with tutorials for easy setup of new Spring applications. Spring boot helps you get started quickly with its auto-configuration ability, and Spring Cloud Microservices interview questions & answers extends Spring Boot with cloud &

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30+ Java Code Review Checklist Items

This Java code review checklist is not only useful during code reviews, but also to answer an important Java job interview question,

Q. How would you go about evaluating code quality of others’ work?

You also learn a lot from peer code reviews. What has been written well?

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6 Key considerations in processing large files in Java

Q1. What are the key considerations in processing large files?
A1. Before jumping into coding, get the requirements.

#1 Trade-offs among CPU, Memory Usage & Disk I/O

Processing a file involves reading from the disk, processing (e.g. parsing an XML and transforming), and writing back to the disk.

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8 JEE (i.e. Java EE) Overview interview Q&As

This is JEE from a 10,000 feet before diving into details of each technology.

Q1. When a company requires Java EE experience, what are they really asking for?
A1. Java EE (i.e. Enterprise Edition) is a collection of specifications for developing and deploying enterprise applications.

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9 Java Garbage Collection interview questions & answers to ascertain your depth of Java knowledge

Java Garbage Collection interview questions & answers to ascertain your depth of Java knowledge in building industry strength Java applications.

Q1. In which part of memory does Java garbage collection (i.e. GC) occur? When does the garbage collection occur? In which thread does the GC run?

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Beginner array coding problems in Java

More Data Structure and Algorithms Coding Questions and answers in Java.

Q1. Write a program that allows you to create an integer array of 5 elements with the following values: int numbers[ ]={5,2,4,3,1}. The program computes the sum of first 5 elements and stores them at element 6,

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Converting a BST Tree to a List in Java

This is the reverse of Converting an Array/List to BST in Java. It is a very common task to convert a collection type A to B as a developer. More examples to practice: Converting from A to B

There are 3 ways to traverse a tree to flatten it to a list


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Finding the missing numbers Java example

Q. Can you write code to identify missing numbers in a given array of numbers?

Solution 1: Assuming that the given numbers are in order


The above solution assumes that the numbers are in order (i.e.

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Java coding practice problems – prime and powerful

There is no other way to pass the Java coding tests other than practicing. I have failed Java coding tests due to lack of practice. How often do you get work with tree and graph data structures? Ho often do you work with algorithms?

50+ Java coding practice problems Links:

Can you write code in Java?

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Part 1: Badly designed Java classes & interfaces

4 Part practical design concept series

Part 1: Abstraction | Part 2: Single Responsibility Principle | Part 3: Open Close Principle | Part 4: Dependency Inversion Principle.

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Q1-Q10: Top 50+ Core Java interview Q&As

These are must know Java interview FAQs. If you don’t get these Java interview questions right, you will not be getting an offer.

Q1. What is the difference between “==” and “equals(…)” in comparing Java String objects?
A1. When you use “==” (i.e.

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Top 15 slacknesses that can bite you as an experienced programmer or architect

Production issues seek the attention of middle and top level management. Here are a few things that you must pay attention as a software developer or architect to prevent any future embarrassments. You can use this as a check list.

#1: Not externalizing configuration values in config file(s) (E.g: .properties,

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Why do Proxy, Decorator, Adapter, Bridge, and Facade design patterns look similar? What are the differences?

There are often patterns that look very similar, but differ in their intent. Most patterns use polymorphism with interface inheritance. Strategy and state design patterns are very similar as well. Proxy, Decorator, Adapter, and Bridge are all variations on “wrapping

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Why favor composition over inheritance? A popular interview question

One of the most popular Java OOP Interview Questions & Answers asked 90% of the time in job interviews is why favor composition over inheritance? The correct answer depends on the problem you are trying to solve, and the answer you give lead to more follow up questions to test your understanding of OOP as described below in detail.

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⏯ Java high-level architecture & Integration Styles Interview Q&As Video

Links to Java Architecture Q&As

Java/JEE integration styles interview questions and answers
Java/JEE Architecture overview interview questions and answers

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