This page lists all Java interview preparation topics in a structured, reference-style format. Each topic links to a dedicated interview page covering questions, scenarios, and common pitfalls.
Core Java – Foundation
- Java Introduction
- Java Features
- Why Java is Platform Independent
- Java Architecture Overview
- Java Program Execution Flow
- public static void main Method
- Command Line Arguments in Java
- JVM JDK JRE Differences
- Bytecode in Java
- ClassLoader Basics
- Heap vs Stack Memory
- Primitive Data Types in Java
- Wrapper Classes in Java
- Autoboxing and Unboxing
- Java Keywords
- static Keyword in Java
- final Keyword in Java
- this Keyword in Java
- super Keyword in Java
- Java Naming Conventions
Core Java – OOP & Collections
- Object Oriented Programming Concepts in Java
- Classes and Objects in Java
- Constructors in Java
- Constructor Overloading
- Inheritance in Java
- Polymorphism in Java
- Method Overloading vs Overriding
- Abstraction in Java
- Encapsulation in Java
- Interface in Java
- Abstract Class in Java
- IS-A vs HAS-A Relationship
- Composition vs Inheritance
- String Immutability
- String vs StringBuilder vs StringBuffer
- equals() and hashCode Contract
- HashMap Internal Working
- HashMap vs Hashtable
- HashMap vs ConcurrentHashMap
- ConcurrentModificationException
Concurrency & JVM
- Multithreading in Java
- Thread vs Process
- Thread Lifecycle
- synchronized Keyword
- volatile Keyword
- Deadlock in Java
- Race Condition in Java
- wait() notify() notifyAll()
- ExecutorService in Java
- ThreadPoolExecutor Internals
- ForkJoinPool in Java
- Callable vs Runnable
- Atomic Variables in Java
- JVM Memory Model
- Garbage Collection in Java
- OutOfMemoryError Analysis
- Memory Leaks in Java
- Soft Weak Phantom References
- JIT Compiler in Java
- Reflection API Basics
Advanced Core Java
- Producer Consumer Problem
- Custom Exception Design
- Checked vs Unchecked Exceptions
- final vs finally vs finalize
- Serialization in Java
- transient Keyword
- Cloneable Interface
- Shallow Copy vs Deep Copy
- Immutability Design in Java
- LRU Cache Implementation
- Thread Safe Singleton
- ClassLoader Hierarchy
- Metaspace vs PermGen
- JVM Tuning Basics
- Java Performance Optimization
Expert Java & System Design
- Garbage Collector Comparison
- G1 vs ZGC vs Shenandoah
- High Performance Java Design
- Object Pooling in Java
- Caching Strategies in Java
- Low Latency Java Systems
- Java Memory Optimization
- Concurrency Design Patterns
- Scalability in Java Applications
- Java System Design Interviews
Java Design Patterns
- Singleton Design Pattern
- Factory Design Pattern
- Abstract Factory Pattern
- Builder Pattern
- Prototype Pattern
- Adapter Pattern
- Bridge Pattern
- Composite Pattern
- Decorator Pattern
- Facade Pattern
- Proxy Pattern
- Chain of Responsibility Pattern
- Observer Pattern
- Strategy Pattern
- Template Method Pattern
- Command Pattern
Interview Gap-Filling Topics (Why / Trade-offs)
- Why HashMap Is Not Thread-Safe
- Why String Is Immutable in Java
- Why equals and hashCode Must Be Overridden Together
- Why Java Does Not Support Multiple Inheritance
- Why Composition Is Preferred Over Inheritance
- Why wait notify Are Defined in Object Class
- Why volatile Does Not Guarantee Atomicity
- Why synchronized Reduces Performance
- Why Java Uses Pass-by-Value Only
- Why Thread.stop Is Deprecated