1
Core Java Fundamentals
Level: Beginner → Intermediate. Learn Java philosophy, JDK vs JRE vs JVM, Java Memory Model, variables, string handling, wrapper classes, final keyword, pass-by-value concept, and garbage collection basics.
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Learning objectives:
• Understand Java Philosophy – Write Once, Run Anywhere
• Learn JDK vs JRE vs JVM
• Master Java Memory Model (Heap & Stack)
• Understand Variables (Local, Instance, Static)
• Learn == vs equals()
• Master String, StringBuilder, StringBuffer
• Understand Wrapper Classes & Autoboxing
• Learn final keyword
• Understand Pass-by-Value Concept
• Learn Garbage Collection Basics
2
Object-Oriented Programming (OOP)
Level: Beginner → Advanced. Master the four pillars of OOP, encapsulation, inheritance vs composition, polymorphism, abstraction, method overloading vs overriding, static vs instance members, and SOLID design principles.
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Learning objectives:
• Master Four Pillars of OOP
• Understand Encapsulation with real examples
• Learn Inheritance vs Composition (Real-world design)
• Master Polymorphism (Why it matters in production)
• Understand Abstraction – Abstract Class vs Interface
• Learn Method Overloading vs Overriding
• Understand Static vs Instance members
• Introduction to SOLID design thinking
3
Collections Framework
Level: Intermediate → Advanced. Deep dive into Collection hierarchy, List vs Set vs Map, ArrayList vs LinkedList performance, HashMap internal working, ConcurrentHashMap, and null handling in collections.
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Learning objectives:
• Understand Collection Hierarchy
• Learn List vs Set vs Map
• Master ArrayList vs LinkedList (Performance truth)
• Understand HashMap internal working
• Learn HashMap vs LinkedHashMap vs TreeMap
• Master Comparable vs Comparator
• Understand Iterator vs ListIterator vs Enumeration
• Learn ConcurrentHashMap vs HashMap vs Hashtable
• Understand Null handling in collections
4
Exception Handling
Level: Intermediate. Learn checked vs unchecked exceptions, try-catch-finally, try-with-resources, exception propagation, custom exceptions, and exception handling best practices.
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Learning objectives:
• Understand Checked vs Unchecked Exceptions
• Master try-catch-finally
• Learn try-with-resources
• Understand Exception Propagation
• Create Custom Exceptions
• Learn Exception Handling Best Practices
• Master Logging & rethrowing strategy
5
Multithreading & Concurrency
Level: Advanced. Master thread creation, synchronized keyword limitations, volatile keyword, Java Memory Model & Happens-Before, Thread Pools, ExecutorService, CountDownLatch, CyclicBarrier, Semaphore, and deadlock prevention. High interview value for product companies.
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Learning objectives:
• Learn Thread creation methods
• Understand synchronized keyword limitations
• Master volatile keyword
• Learn Java Memory Model & Happens-Before
• Understand Thread Pools & ExecutorService
• Learn ThreadPoolExecutor internals
• Master CountDownLatch
• Understand CyclicBarrier
• Learn Semaphore
• Master Deadlock & Prevention techniques
6
Java 8+ Features
Level: Intermediate → Advanced. Master Lambda expressions, functional interfaces, Stream API, Map/Filter/Reduce, Optional class, parallel streams, records, pattern matching, and modern Java coding style.
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Learning objectives:
• Master Lambda Expressions
• Understand Functional Interfaces
• Learn Stream API
• Master Map, Filter, Reduce
• Understand Optional Class
• Learn Parallel Streams
• Master Records
• Understand Pattern Matching
• Learn Modern Java coding style
7
Spring Framework Core
Level: Intermediate. Understand why Spring exists, IoC & Dependency Injection, ApplicationContext, Bean Lifecycle, Bean Scopes, component annotations, constructor injection, and Spring AOP basics.
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Learning objectives:
• Understand Why Spring exists (Problems it solves)
• Master IoC & Dependency Injection
• Learn ApplicationContext
• Understand Bean Lifecycle
• Learn Bean Scopes
• Master @Component vs @Service vs @Repository
• Understand Constructor Injection (Best practice)
• Learn Spring AOP basics
• Understand Cross-cutting concerns
8
Spring Boot
Level: Intermediate. Learn why Spring Boot, auto-configuration, starter dependencies, application properties, profiles (dev/prod), actuator basics, and exception handling in Spring Boot.
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Learning objectives:
• Understand Why Spring Boot
• Master Auto-configuration
• Learn Starter dependencies
• Configure Application properties
• Understand Profiles (dev/prod)
• Learn Actuator basics
• Master Exception handling in Spring Boot
9
Spring Security
Level: Intermediate. Master authentication vs authorization, Spring Security flow, filters & security context, password encoding, and role-based access control.
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Learning objectives:
• Understand Authentication vs Authorization
• Learn Spring Security flow
• Master Filters & Security Context
• Learn Password encoding
• Understand Role-based access control
10
RESTful Web Services
Level: Intermediate. Learn REST principles, HTTP methods, REST annotations, request & response handling, exception handling in REST, and best practices.
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Learning objectives:
• Understand REST principles
• Master HTTP methods
• Learn REST annotations
• Understand Request & Response handling
• Master Exception handling in REST
• Learn Best practices
11
Database & JPA / Hibernate
Level: Intermediate → Advanced. Master ORM concepts, JPA vs Hibernate, entity lifecycle, fetch types, lazy vs eager loading, JPQL, N+1 problem, and transactions.
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Learning objectives:
• Understand ORM concepts
• Learn JPA vs Hibernate
• Master Entity lifecycle
• Understand Fetch types
• Learn Lazy vs Eager loading
• Master JPQL
• Understand N+1 problem
• Learn Transactions
12
Testing
Level: Intermediate. Learn unit testing basics, JUnit, Mockito, mocking dependencies, and testing Spring components.
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Learning objectives:
• Understand Unit Testing basics
• Master JUnit
• Learn Mockito
• Understand Mocking dependencies
• Learn Testing Spring components
13
Build Tools
Level: Beginner. Learn Maven lifecycle, pom.xml, dependencies & plugins, and Gradle basics.
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Learning objectives:
• Understand Maven lifecycle
• Learn pom.xml
• Master Dependencies & plugins
• Learn Gradle basics
14
Design Patterns
Level: Intermediate → Advanced. Understand why design patterns matter, and learn Singleton, Factory, Builder, Strategy, Observer, Adapter patterns with real-world usage.
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Learning objectives:
• Understand Why Design Patterns
• Master Singleton
• Learn Factory
• Understand Builder
• Master Strategy
• Learn Observer
• Understand Adapter
• Learn Real-world usage
15
System Design & Architecture
Level: Advanced. Master layered architecture, hexagonal architecture, event-driven architecture, CQRS, API Gateway, circuit breaker, saga pattern, caching strategies, and message queues.
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Learning objectives:
• Understand Layered Architecture
• Learn Hexagonal Architecture
• Master Event-Driven Architecture
• Understand CQRS
• Learn API Gateway
• Master Circuit Breaker
• Understand Saga Pattern
• Learn Caching Strategies
• Master Message Queues
16
Docker & Containerization
Level: Beginner. Learn what Docker is, containers vs VMs, Dockerfile basics, and Java app containerization.
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Learning objectives:
• Understand What is Docker
• Learn Containers vs VMs
• Master Dockerfile basics
• Learn Java app containerization
17
Practical Coding Problems
Level: Interview-Focused. Solve practical coding problems including second largest number, palindrome check, duplicate elements, thread-safe counter, reverse linked list, Two Sum, LRU Cache, Producer–Consumer, and Rate Limiter.
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Learning objectives:
• Solve Second largest number
• Master Palindrome check
• Handle Duplicate elements
• Implement Thread-safe counter
• Learn Reverse linked list
• Solve Two Sum problem
• Implement LRU Cache
• Master Producer–Consumer pattern
• Implement Rate Limiter
18
Advanced Interview Concepts
Level: Advanced. Master sync vs async decision making, production debugging, good code vs production-ready code, performance optimization, and security best practices.
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Learning objectives:
• Understand Sync vs Async decision making
• Master Production debugging
• Learn Good code vs Production-ready code
• Understand Performance optimization
• Master Security best practices