Core Java Fundamentals JVM, JDK, JRE architecture & lifecycle
Compilation: javac bytecode JVM
Memory model: Stack vs Heap
Key concepts: final/finally/finalize, static, volatile, String immutability
Object-Oriented Programming
(OOP)
4 Pillars: Encapsulation, Abstraction, Inheritance, Polymorphism
Overloading vs Overriding, Abstract vs Interface
Multiple inheritance via default methods, DTO usage
Collections Framework List, Set, Map — internal logic & use cases
ArrayList vs LinkedList, HashMap internals
hashCode() & equals(), ConcurrentHashMap, Generics
Java 8+ Features Lambdas, Functional Interfaces, Streams API
Optional class, Method References
Predicate, Function, Consumer — key interfaces
Contemporary Java (11–21) Sealed classes, Records, Text blocks
var keyword, Pattern Matching, Switch enhancements
Exception Handling Checked vs Unchecked, Multi-catch, Custom exceptions
Common errors (NPE, OOM), Best practices

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