Java developer

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

Modern 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