. . .

session 1

What is Java variables and How to declare Java variables?
What are Java data types?
What are Primitive data types in Java?
What is wrapper class in Java and Why we need wrapper class?
What is the differences between passing by value and passing be reference?
What is an Immutable class in Java?
How to create a custom immutable class in Java?
What is String pool in Java and why we need String pool?
What are the results of following expressions? Please include the calculation process.
- 5 & 6
- 5 | 6
- 5 ^ 6
What is toString() and why we need it?
OutOfMemoryError vs StackOverflowError vs Memory Leak
How to make class immutable?
How does string works? Why is String immutable in Java?
What’s Garbage collection types and Whats new in java 8?
JDK vs JRE vs JVM

session2

What is static field and static method?
What is Object in Java and why we need object?
What is Inheritance and how many types of inheritance are supported by Java?
What is Interface and what is abstract class? What are the differences between them?
What is Polymorphism? And how Java implements it?
What is the differences between overriding and overloading?
What is Encapsulation? How Java implements it? And why we need encapsulation?
What is the difference between abstraction and encapsulation?
Can we use this keyword in constructor and why?
Abstract class vs. Interface. When to use abstract class and when to use interface?
Generics and how do you use generics in your project?
Java OOP 4 principles, and explain each of them
Serialization, What is Serializable and SerialVersionUID?
why using static and why not?
what is SOLID principle?
What is externalization and its difference with serialization
Basic principles of the OOP
Why Inheritance? / Benefit of using Inheritance
Inheritance vs. Composition/Aggregation -> IS-A and HAS-A
Can a class inherits multiple parent classes? / Is multiple inheritance allowed? Why?

session3

Describe the Collections Type Hierarchy. What Are the Main Interfaces, and What Are the
Differences Between Them?
What are List interface implementations and what are the differences between them and
when to use what?
What are Queue interface implementations and what are the differences and when to use
what?
What are Set interface implementations and what are the differences and when to use
what?
Explain the structure of the Deque implementation of LinkedList and its usage.
What are the differences between HashMap, LinkedHashMap and TreeMap?
What is the hashCode() and equals() function?
How Is HashMap Implemented in Java? How Does Its Implementation Use hashCode and
equals Methods of Objects? What Is the Time Complexity of Putting and Getting an
Element from Such Structure?
What are the differences between SynchronizedMap and ConcurrentHashMap?
HashMap: how does it work internally, what is hash collision
HashTable vs. HashMap
ArrayList vs LinkedList, which one to choose?
How does arraylist work internally?
How does ConcurrentHashMap works?
Relationship between equals() and hashcode()
Difference between HashSet and TreeSet, HashMap and TreeMap
What is fail-fast and fail-safe?
HashMap vs LinkedHashMap and HashSet vs LinkedHashSet
Suppose when you have Employee class to store data, when do you use list or map
Difference: Arraylist vs LinkedList, when to use which
Difference between Iterator and Enumeration

Session4

What is Builder Pattern and why we need it?
What is an exception and what is an error in Java? What are the differences
between them?
What are the types of exceptions in Java? What are the differences?
How can we handle an exception in Java?
What is a custom exception and why do we need to use it?
What is the difference between the final and finally keywords?
Is the following code legal?Why?
Try{
}finally{
}
Is there anything wrong with the following exception handler as written? Will this code compile?
Match each situation in the first list with an item in the second list.
a. Scenarios
i. int number = “four”;
ii. public void recursion() { recursion(); }
iii. A program is reading a stream and reaches the end of the stream marker.
iv. You write code to read from a file but misspelled the filename
b. Exceptions/Errors
i. Error
ii. checked exception
iii. compile error
iv. no exception
What is Proxy Design Pattern?
What is a Singleton class?
Types of Exceptions and how do you deal with exceptions in your project?
Implement a singleton
Explain the Factory design pattern
What design patterns did you worked on before?
How to custom an Exception?
What is ConcurrentModificationException and how to handle it?

Session5

What is Thread and What is Process? What are differences between them?
How to create threads in Java?
Runnable or Thread, which do you prefer to using? Why?
What are differences between start() and run()?
What if invoking start() method of a thread twice? What if invoking run() method twice?
What is Thread Life Cycle in Java? Explain how to get to each stage.
Explain join() method in Java Thread.
What are differences sleep() and wait()?
What is Daemon thread in Java? Why do we need it?
What is thread interference? Give an example.
What are some of the ways to perform Thread Synchronization?
What is Deadlock? How to resolve it?
What is the difference between Runnable and Callable interface?
What is ExecutorService?
Describe when you would use @Async and ExecutorService to improve
the performance of your web application.
Explain the usage of get() and join() in ExecutorService, what is the
difference between them?
Explain the difference between Future and CompletableFuture.
Do you know about the Executor Service and Future?
How do you create a thread?
How does thread communicate/interact/share data with each other?
What are the meaning of thread methods: join, wait, sleep, yield
What is the deadlock? How to FIND it? How to avoid it?
How to make a global count in multithreading environment
Difference: Synchronized, ThreadLocal, Volatile, AtomicInteger
Difference: Sleep and Wait
Difference runnable vs callable
Difference future vs completableFuture
How do you implement a deadlock
Synchronized method vs Synchronized block
What is difference between synchronized and ReentrantLock

Session6

1) What is the Stream API in Java 8? What are the differences between

intermediate and terminal operations for Stream?
1) What is the Optional class in Java and why do we need it?
New feature of Java 8. Give an example of how you use them in your project
If java 8 allows default method in interface, so what is the real difference between interface and
abstract class?
What is the Functional Interface? Java 8 built in functional interface? Match each situation in the first list with an item in the second list.
- a. Scenarios
  - i. int number = “four”;
  - ii. public void recursion() { recursion(); }
  - iii. A program is reading a stream and reaches the end of the stream
  - marker.
  - iv. You write code to read from a file but misspelled the filename
- b. Exceptions/Errors
  - i. Error
  - ii. checked exception
  - iii. compile error
  - iv. no exception
Explain Marker Interface. (Please also name some built-in marker interfaces provided in Java.)
Why we need to use break statement in Switch statement?
What are access modifiers and their corresponding scopes in Java?
Explain the main method in Java.
What is the diamond problem in Java? And how can we resolve the problem?
What is Comparable and Comparator interface? What are differences between them and
how to use them?
What is Functional Interface? How do you create your own Functional Interface?
What is Lambda Expression? Why does Lambda Expression work so closely with
Functional Interface?
java 8: Different types of “method reference”
What is Optional?
Java 8: Intermediate operator and terminal operator in stream api
Map vs. FlatMap
Java switch statement has too many cases, how to improve it
Comparable vs. Comparator
New features in java 11 and 17
What is Java 17 new feature - sealed class

Session7

What is data modeling? Why do we need it? When would you need it?
What is primary key? How is it different from unique key?
How do you represent a multi-valued attribute in a database? Please describe in detail
using an example.
How do you represent a many-to-many relationship in database? Please describe in detail
using an example.
What is normalization? Why do you need to normalize?
What does data redundancy mean? Can you give an example of each?
What are normal forms?
What is database integrity? Why do you need it?
What are joins and explain different types of joins in detail.
Explain indexes and why are they needed?
Explain clustered and non-clustered index and their differences.
If we have 1B data in our relational database and we do not want to fetch all at once. What
are the ways that we can partition the data rows?
Different type of Joins.
Write a query: find the most popular product of one month.
Explain ACID concepts
What database did you use and how do you communicate with the DB
Find the 2nd largest salary in employee table.
Find employee whose salary is higher than its own manager(only given employee table which
contains employee id and its manager id)
Given employee table contain employee id, name,salary and manager id, find the employee
whose salary is higher than their manager.
How to delete duplicate rows, only keep unique rows
Given 2 tables, find the data in both of table that not matching each other
PreparedStatement vs Statement vs Callable Statement

Session8

Explain relational database and non-relational database.
Difference between SQL and NoSQL.
Explain CAP Principal.
What is ACID?
How do you decide which database to choose, SQL or NoSQL
Explain CAP theorem and which database use them
How to find all available keyspaces in Cassandra
What is consistent hashing in cassandra
what is cassandra replication strategy
What is sharding in MongoDB?
How replication works in MongoDB

Session9

What is RESTful Web Service?
How to create a controller?
Describe the RESTful principles.
How does the RestTemplate work.
What is difference between path variable and query param?
Http status code you ever met.
Explain MVC and the order of each components.
Different types of request mapping/rest api/http methods.
Comparison between soap and rest.
When designing a public API, what needs to be considered.
If define a object in the controller, and then other request update the value of the object, then
which value will be fetched by a new request?
Explain the differences between REST and SOAP.
Explain the usage of @RestController.
Explain the difference between @RequestBody and @ResponseBody
How can we communicate with external applications in our Spring application?
How to handle controller exceptions? How spring handles exception?
What will happen after clicking the URL?
Key Difference: Soap vs Rest

Session10

What is Dependency Injection?
What is the di erence between BeanFactory and ApplicationContext in Spring?
How Can We Inject Beans in Spring?
Which Is the Best Way of Injecting Beans and Why?
What is the Scope of a Bean?
How Does the Scope Prototype Work?
What Does the Spring Bean Lifecycle Look Like?
Explain different ways to solve the bean ambiguity when we try to inject dependencies.
When there is circular dependency, use which type of injection?
Setter based Injection VS. Constructor based?
Explain DispatcherSeervlet in detail
ApplicationContext VS. BeanFactory
How to inject beans when there are two beans with the same type?
Spring validation?
How to make a java class managed by spring?
How does spring injection singleton bean into prototype bean?
How to let spring create a bean only when that bean is needed instead of create at beginning
What about lazy loading a spring bean?
Spring literal and new and intern() objects
Why is spring immutable in java?
How do you use cache in your whole project?
Spring Annotation you used in your project?
What is conditional bean in Spring boot?
What is IoC/Dependency Injection?
Spring bean annotation, bean life cycle and bean scope
Spring Bean scope and explain the request scope
Different ways of DI
Difference between @Component and @Bean
When there is circular dependency, use which type of Injection? / Setter based Injection vs.
Constructor based

Session12

What is Spring Boot? How does it differ from Spring?
What is Spring Retryable?
Why do you use Spring Boot? / Benefits of Spring Boot
How to start a Spring Boot project?
Command to run a spring boot application
What does @SpringBootApplication mean?
For Spring Boot, how do I use another server such as WebLogic instead of the embedded
Tomcat server?
Regarding @Async 1) what is it for 2) how to define it 3) how to call async method 4) can async
method be private and why
Difference between Spring boot and Spring
How to do cache in spring boot and how to refresh the cache

Session13

What is AOP and why do we need it?
What is Join Point?
What is Point Cut?
What is Advice?
How do you handle exceptions in your Spring Application?
What is AOP and how do you implement AOP in the project?

Session14

What are JDBC statements? List all types of JDBC statements and their usage.
What is JdbcTemplate? And what are some of the advantages it has over standard JDBC?
What is ORM and why is it helpful?
What is Hibernate and what are the advantages of Hibernate over JDBC?
What is a Session and how do we get a Session?
If an application uses Hibernate for persistent logic and uses MySQL as persistent store,
what are the steps that we need to do if the application want to switch to OracleDB from
MySQL? (Assume table structures remain the same)
What is a SessionFactory and how do we get a SessionFactory?
Ways to connect to database?

Session15

What is “Offline Transaction”?
How do we usually perform Transaction Management in JDBC?
What is Database Transaction? How do you implement transaction?
What are entity states defined in Hibernate / JPA?
How can we transfer the entity between different states?
What are differences between save, persist?
What are differences between update, merge and saveOrUpdate?
How do you use elasticSearch in your java application
How does hibernate internally check if entity version has changed?
How to configure multiple database using JPA?

Session16

Explain the difference between authentication and authorization.
What is JWT?
What is Spring Security and what can it help us to achieve?
How do we secure a RESTful API?
Have you used security? how do you protect your rest api? how do you protect your
application?
How do you implement security for your application or microservices

Session17

Explain and name some methods that you used in JUnit.
Explain and name some annotations that you used in JUnit.
What is Mockito and the usage of it?
What kind of test experience do you have?
Cucumber and its annotations.
How cucumber works, give an example.
Functional test & Integration test & Unit test
What’s the test framework in your team?
Talk about different test you did before.
Junit VS. Automation
What is the limitation of the Mockito?
Can you mock a static field using Mockito?
How to test a private method without other framework?
Difference: InjectMock VS. InjectMockBean?

Session19

In your own word, please describe some of the advantages and disadvantages of a
Monolithic Application.
In your own word, please describe some of the advantages and disadvantages of a
Microservice Application.
What is the purpose of using Netflix Eureka?
How can microservices communicate with each other?
What is the purpose of using Spring API Gateway?
Explain cascading failure in microservice and how to prevent it.
Explain CircuitBreaker and how it works in detail.
How much load can your API handle at the same time? What is your RPS
When your frontend or rest api loads slowly, how do you solve it?
How to monitor the status of the application?
What application details are stored in service registry?
How can you make services communicate with each other? -> Tools like Spring Cloud to setup
microservice or use message queue like Kafka
How to use the Zuul Gateway API? / How does the Zuul Gateway API work?
How to manage the entire transaction across different microservices? How to rollback?
How to communicate between microservices
Explain microservice
What microservice did your team use?
Disadvantage of microservice
Synchronous communication and A-Synchrounous commuication in microservice->
RestTemplate or feign and message queue like Kafka
vertically and horizontally
How to deploy microservices to AWS EC2?
What type of application is suitable for microservice architecture? What type is not?
Suppose you have two Eureka servers, how does each application know which Eureka server it
is registered to?
What is the circuit breaker?
How does microservices communicate with each other?
How do you use RestTemplate?
How do you get noticed when a service is down?
How to setup service discovery?
What is Granuarity Line in microserivce
How check services and their status, what is they are hosted in docker
How do you config for multiple environments?

Session20

Use your own words to explain Kafka.
Did you use Kafka in your project? How does it work?
Talk about Kafka and Zookeeper
How to start and stop kafka server?
How to prevent data loss in kafka
How to keep message order in Kafka
Kafka how to let two consumers read the same message
Kafka how to determine the consumption rate

session22

How do you monitor your application? Please provide examples.
Explain the difference between these log levels: INFO, WARN, ERROR.
If you have error, but it is not showing in log, how do you debug and find it?
How to prevent duplicate message in kafka
What is kafka dead letter queue and how do you handle it?
How to implement security to kafka. Kafka Security

Session23

Use your own words to explain Jenkins.
Can you talk about CI/CD?
Git command you used in the project
How do you release from the git repository
How do you combine several commits together
What is git cherry-pick
difference between git and svn
difference git merge and rebase

Session24

How to deploy microservice in AWS container

Session25

AWS difference between parameter store and secret manager
AWS where to store certificate file

extra

(those we are not sure which session to put in)

Use your own words to explain TDD and why use TDD.
Please do some research on Redis and use your own words to explain what Redis is.
Use your own words to explain what Swagger is.
Please do some research on ELK and use your own words to explain what they are.
Use your own words to explain Jira.
What is RabbitMQ and what can it help us to achieve in a web application?
What are the component of RabbitMQ?
What are different types of Exchange that exist in RabbitMQ?
What is Scheduler and what can it help us to achieve in a web application?
What is Maven and why it is used?
What is POM? And what information does POM contain?
What is Maven Repository? What is Maven Central Repository? What is local Maven
Repository?
What is JAR and WAR? What are the di erences?
What is Connection Pool and its advantages?
What are some of the configurations for Connection Pool?
Difference between get and load?
What is flush method? Why do we need it?
What is evict method? Can you provide an example where you used it?
How to use docker in the Spring Boot?
ElasticSearch why do you use it
How does Java class loader work?
Shallow copy vs. Deep copy
When implements Serializable, what if you don’t define the serialVersionUID? What if you
remove it?
Design a Employee Voting system according to the requirements
Design a parking lot according to the requirements
When you API request or Frontend page loading slowly, how do you handle it?