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Interview questions with answers, clear comparisons and roadmaps. Each guide links to the lessons that teach it step by step.
The questions interviewers ask most, with short answers and runnable code.
35 Java interview questions for freshers with short, clear answers and runnable code: basics, OOP, strings, exceptions, collections, Java 8 and threads.
18 min read
32 OOP interview questions in Java with clear answers and runnable code: classes, encapsulation, inheritance, polymorphism, interfaces and equals.
16 min read
29 Java collections interview questions with clear answers and code: ArrayList, HashSet, HashMap internals, TreeMap, Comparator and concurrent maps.
15 min read
30 Java multithreading interview questions with answers and code: threads, synchronized, volatile, locks, executors, CompletableFuture and deadlocks.
16 min read
30 Spring Boot interview questions with clear answers and code: dependency injection, auto-configuration, REST controllers, JPA, transactions, security.
17 min read
25 SQL interview questions for Java developers with answers and queries: joins, second highest salary, window functions, indexes, transactions.
15 min read
31 Java interview questions for developers with about 2 years experience: collections internals, streams, concurrency, JVM, Spring Boot and design.
18 min read
Clear side-by-side explanations of the topics people mix up.
HashMap vs TreeMap vs LinkedHashMap in Java: order, speed, null keys and when to use each, with a comparison table and runnable examples.
9 min read
Java 8 features with runnable examples: lambdas, functional interfaces, method references, streams, Optional, default methods and the date-time API.
12 min read
ArrayList vs LinkedList in Java: how each works inside, time complexity, memory use and when to choose which, with a comparison table and runnable code.
8 min read
Abstract class vs interface in Java: the differences, what changed in Java 8, when to use each, with a comparison table and runnable examples.
8 min read
== vs equals() in Java: reference versus content comparison, the string pool, Integer caching and writing your own equals(), with examples.
8 min read
String vs StringBuilder vs StringBuffer in Java: immutability, speed, thread safety and when to use each, with a comparison table and runnable examples.
7 min read
Checked vs unchecked exceptions in Java: the exception hierarchy, when the compiler forces handling, examples of each and designing your own exceptions.
8 min read
Comparable vs Comparator in Java: natural order versus custom order, compareTo and compare, multi-field sorting, with a comparison table and examples.
8 min read
What to learn, in what order, and how to get ready for your first job.
A step-by-step Java roadmap for freshers: what to learn in each stage, in what order, which projects to build and how to get ready for interviews.
10 min read
A step-by-step DSA in Java roadmap: what to learn in order, the patterns that matter, how to practise and how to track progress.
11 min read
A step-by-step Spring Boot roadmap: what to learn before Spring, then REST APIs, JPA, security, testing and deployment, with projects for each step.
10 min read
How to prepare for Java placements: the usual hiring rounds, what each tests, a week-by-week plan, resume and project tips, and mistakes to avoid.
11 min read
Java project ideas for students by level: console apps, OOP and collections projects, file and threading projects, and Spring Boot APIs for your resume.
9 min read