Home › Java › 300+ Java Interview FAQs › Archive for Java FAQs – 03: Core Java
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00: Top 50+ Core Java interview questions & answers for 1 to 3 years experience

Top 50 core Java interview questions covering Java core concepts with diagrams, code, examples, and scenarios. If you don’t get these Java interview questions right, you will not be getting an offer.

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00: Top 50+ Core Java interview questions answered – Q11 to Q23

The focus is on Java OOP interview questions and answers. Q11. What is the difference between constructors and other regular methods? A11. Constructors must have the same name as the...

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00: Top 50+ Core Java interview questions answered – Q24 to Q36

Focus is on Java classes, interfaces and generics the interview questions and answers style. Java classes and interfaces are the building blocks. Q24. … Read more ›...

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00: Top 50+ Core Java interview questions answered – Q37 to Q42

As a Java developer, you may not need to know how the JVM works, but the most important topic that you must know is Java Garbage Collection. How the Garbage...

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00: Top 50+ Core Java Interview questions answered – Q43 to Q54

Q43. What can you tell about the performance of a HashMap compared to a TreeMap? Which one would you prefer? A43. … Read more ›...

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01: 15+ Java multithreading interview questions & answers

Multithreading is one of the important features of Java, and multithreading interview Q&As can reveal a lot about your depth of core Java knowledge. Most importantly, it is not easy to grasp multithreading concepts without lots of hands-on experience.

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02: 10 Java String class interview Q&As

Java Recursion - String example

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.

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02: 5 Java multithreading scenarios interview Questions & Answers

Java interview questions & answers on multithreading scenarios to judge your experience in building applications with concurrency in mind. Q1. Can you give some scenarios where you built concurrent systems?...

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03: 7 Things you must know about Java locks and synchronized key word

7 Things you must know about Java locks and synchronized key word summarizes the key basics. #1. Each Java class and object (i.e. … Read more ›...

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03: Understanding Big O notations with Java

Q1.  Have  you seen job advertisements requiring Java candidates to work in real-time or high volume transaction processing systems? A1.  If you are applying for such jobs, … Read more ›...

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300+ Java Interview FAQs
Java FAQs - 01: Prepared?
(2)
Java FAQs - 02: Ice Breaker
(5)
Java FAQs - 03: Core Java
(15)
Java FAQs - 04: OOP & FP
(10)
Java FAQs - 05: JEE
(12)
Java FAQs - 06: Spring
(8)
Java FAQs - 07: Hibernate
(4)
Java FAQs - 08: Web Services
(6)
Java FAQs - 09: Microservices
(12)
Java FAQs - 10: Messaging
(3)
Java FAQs - 11: Architecture
(5)
Java FAQs - 12: RDBMS
(2)
Java FAQs - 13: SQL
(6)
Java FAQs - 14: Code Quality
(4)
Java FAQs - 15: Key Areas
(15)
Java FAQs - 16: UML
(1)
Java FAQs - 17: GIT
(4)
Java FAQs - 18: Unix
(3)
Java FAQs - 19: DevOps (CI/CD)
(9)
Java FAQs - 20: AWS (Cloud)
(5)
Java FAQs - 21: Maven
(1)
Java FAQs - 22: Regex
(2)
Java FAQs - 23: JSON & XML
(3)
Java FAQs - 24: JMeter
(2)
16+ Java Key Areas
Key Area - Going places
(2)
Key Area - Ice Breaker
(6)
Key Area - Design Concepts
(39)
Key Area - Judging Experience
(23)
Key Area - Best Practices
(6)
Key Area - Concurrency Management
(6)
Key Area - Low Latency
(10)
Key Area - CI/CD & DevOps
(13)
Key Area - Debugging
Key Area - Debug Hibernate
(3)
Key Area - Debug Java
(11)
Key Area - Debug JEE
(5)
Key Area - Debug Maven
(1)
Key Area - Debug Spark
(4)
Key Area - Debug Spring
(2)
Key Area - Design Patterns
Key Area - GoF Design
(10)
Key Area - JEE Design
(3)
Key Area - Microservices patterns
(5)
Key Area - Exception Handling
(4)
Key Area - Memory Management
(9)
Key Area - Performance
(13)
Key Area - Scalability
(3)
Key Area - SDLC
(7)
Key Area - Security
(18)
Key Area - Productivity Tools
(23)
Key Area - Transaction Management
(6)
Key Area - QoS & SLAs
(8)
300+ Core Java Interview Q&As
Core Java - Overview
(7)
Core Java - Data types
(9)
Core Java - Constructors
(1)
Core Java - Reserved Key Words
(2)
Core Java - Classes
(3)
Core Java - Objects
(7)
Core Java - OOP
(10)
Core Java - GC
(2)
Core Java - Generics
(5)
Core Java - FP
(14)
Core Java - OOP to FP
(9)
Core Java - I/O
(8)
Core Java - Multithreading
(15)
Core Java - Data Structures
(5)
Core Java - Annotations
(2)
Core Java - AOP
(1)
Core Java - Other
(4)
Core Java - Collection API
(13)
Core Java - Differences X & Y
(5)
Core Java - Event Driven
(2)
Core Java - Exceptions
(1)
Core Java - Java 7
(2)
Core Java - Java 8
(24)
Core Java - Java 9 to 20
(7)
Core Java - JVM
(7)
Core Java - Reactive Program
(3)
Core Java - Swing & AWT
(2)
Core Java - Understanding
(4)
300+ Enterprise Java Interview Q&As
JEE - Overview
(2)
JEE - Web basics
(10)
JEE - Web Services
(11)
JEE - JPA
(2)
JEE - JTA
(1)
Key Area - JEE - API Design
(2)
JEE - JDBC
(5)
JEE - Microservices
(8)
JEE - JMS
(5)
JEE - JMX
(3)
JEE - JNDI and LDAP
(2)
JEE - JSF
(2)
JEE - Other
(3)
150+ Spring & Hibernate Interview FAQs
Framework - Hibernate Q&As
(13)
Framework - Spring Core
(5)
Framework - Spring MVC
(7)
Framework - Spring Cloud
(1)
Framework - Spring boot
(2)
Framework - Spring IO
(1)
Framework - Spring Config
(5)
150+ Java Architect interview FAQs
Architecture - Patterns
(10)
Architecture - How to
(12)
Architecture - AWS
(8)
Architecture - Azure
(6)
Architecture - Distributed
(8)
Architecture - Microservices
(11)
Architecture - Networking
(6)
Architecture - QoS
(1)
Architecture - ERD
(1)
Architecture - ETL
(2)
Architecture - Low Latency
(6)
Architecture - UML
(1)
150+ Companion Tech Interview Q&As
Tech - SQL Interview Q&As
(36)
Tech - Unix interview Q&As
(27)
Tech - Git interview Q&As
(8)
Tech - JavaScript Q&As
(6)
Tech - Regex Interview Q&As
(3)
Tech - XML Interview Q&As
(2)
Tech - JSON interview Q&As
(2)
Tech - Maven interview Q&As
(3)
Tech - NoSQL Interview Q&As
(3)
Tech - Groovy interview Q&As
(7)
Tech - JMeter interview Q&As
(2)
Tech - Domain Knowledge Q&As
(3)
Tech - FIX interview Q&As
(2)
Tech - YAML interview Q&As
(4)
Tech - XSD Interview Q&As
(2)
Tech - JavaScript - Angular JS
(3)
Tech - Networking interview Q&As
(5)
Tech - AWS Cloud
(10)
Tech - Azure Cloud
(4)
Tech - Docker & Kubernetes
(7)
150+ Java code quality interview Q&As
Code Quality - Automation
(1)
Code Quality - Code Coverage
(2)
Code Quality - FAQs 🔥
(7)
Code Quality - Profiling
(3)
Code Quality - Performance Test
(2)
Code Quality - Unit Testing
Code Quality - BDD
(4)
Code Quality - JMockit
(15)
Code Quality - Mockito
(4)
Code Quality - Unit Testing FAQs
(3)
Code Quality – Testing DAOs
(4)
Code Quality – JUnit, Mockito & Spring
(6)
Code Quality – JUnit Web
(2)
Code Quality - Spring TXN
(2)
150+ Java coding interview Q&As
Coding - Can you write code?
(22)
Coding - Complete the code
(13)
Coding - Converting from A to B
(6)
Coding - Designing your classes
(9)
Coding - Data Structures
Coding - Arrays
(2)
Coding - Big O notation
(2)
Coding - Graph Structure
(2)
Coding - LinkedList Structure
(2)
Coding - Map Structure
(1)
Coding - Pointer Algorithms
(3)
Coding - Queue Structure
(1)
Coding - Searching Algo
(1)
Coding - Sorting Algo
(4)
Coding - Stack Structure
(1)
Coding - Tree structure
(14)
Coding - Data Which & Why
(2)
Coding - Passing the unit tests
(5)
Coding - What is wrong?
(10)
Coding - Home Assignments
(6)
Coding - Written Test Core Java
(4)
Coding - Written Test JEE
(1)
Tutorials - Big Data
TUT - ⏯ Starting Big Data
TUT - Starting Spark & Scala
TUT - Starting with Python
TUT - Kafka
TUT - Pig
TUT - Apache Storm
TUT - Spark Scala on Zeppelin
TUT - Cloudera
TUT - Cloudera on Docker
TUT - File Formats
TUT - Spark on Docker
TUT - Flume
TUT - Hadoop (HDFS)
TUT - HBase (NoSQL)
TUT - Hive (SQL)
TUT - Hadoop & Spark
TUT - MapReduce
TUT - Spark and Scala
TUT - Spark & Java
TUT - Apache Kafka
TUT - Hadoop
TUT - PySpark on Databricks
TUT - Zookeeper
Tutorials - Enterprise Java
TUT - ⏯ Starting with Java
TUT - Diagnosis
TUT - Akka
TUT - Akka Scala
TUT - Akka Java
TUT - AWS EC2
TUT - CI/CD Jenkins
TUT - Core Java
TUT - Debugging
TUT - Java 8
TUT - JSON and Java
TUT - Java Beginner
TUT - XML and Java
TUT - CSV and Java
TUT - Docker
TUT - JEE
TUT - Web & Web Services
TUT - REST Client
TUT - JSF
TUT - JDBC
TUT - FIX and Java
TUT - JAXB
TUT - JMX
TUT - JPA
TUT - MySQL
TUT - Scala
TUT - Scala Actors
TUT - Spring & Hibernate
TUT - Hibernate
TUT - Spring Basics
TUT - Spring batch
TUT - Hibernate & Spring
TUT - Spring Boot
TUT - Spring IO
TUT - Spring ORM
TUT - Spring other
TUT - Spring OXM
TUT - Spring Cloud
TUT - Tools
TUT - JMeter
TUT - Maven
TUT - Maven Assembly
TUT - Maven Profiles
TUT - Productivity Tools
TUT - Apache Kafka
TUT - Kubernetes
TUT - ⏯ Videos
TUT - ⏯ Starting with Java
TUT - ⏯ Spring Core
TUT - ⏯ Spring MVC
TUT - ⏯ JDBC, Hibernate
TUT - ⏯ Spring Boot
TUT - ⏯ Angular with Spring
TUT - ⏯ Q&As
TUT - Other
TUT - SQL
TUT - Drools
TUT - Apache POI
TUT - DOS
TUT - Dozer
TUT - ESB
TUT - Groovy
TUT - Jasper Reports
TUT - Logging and auditing
TUT - Metrics
TUT - Orika Mapping
TUT - Pentaho Kettle ETL
TUT - Unix
TUT - Webspeher MQ
TUT - YAML

Prepare to fast-track & go places

Answers are detailed to be useful beyond job interviews. A few Q&As each day will make a huge difference in 3 to 24 months depending on your experience.
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