1. OOP Concepts
- Provide real-world examples and explain usage in code.
2. Java Memory Management
- Stack vs Heap, Garbage Collection, memory leaks, object creation and scope.
3. Exception Handling
- Checked vs Unchecked exceptions
- try-catch-finally, throws vs throw, custom exceptions.
4. Collections Framework
- List, Set, Map interfaces and implementations
- ArrayList vs LinkedList, HashSet vs TreeSet, HashMap vs LinkedHashMap
5. Multithreading and Concurrency
- Thread lifecycle, Runnable vs Thread, synchronization, volatile, wait/notify
- ExecutorService, Callable, Future
