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1. Fundamentals

1.1. Variables and Data Types
1.2. Operators
1.3. Control Flow: if-else
1.4. Control Flow: for Loop
1.5. Arrays

2. Object-Oriented Programming (OOP)

2.1. Classes and Objects
2.2. Inheritance
2.3. Polymorphism
2.4. Encapsulation
2.5. Abstraction

3. Collections Framework

3.1. List and ArrayList
3.2. Set and HashSet
3.3. Map and HashMap
3.4. Iterating Collections

4. Java 8+ Features

4.1. Lambda Expressions
4.2. Stream API
4.3. Optional

Interview Questions

1. What is the difference between JVM, JRE, and JDK?
2. Explain the contract between `equals()` and `hashCode()`.
3. Why are Strings immutable in Java?
4. Differentiate `final`, `finally`, and `finalize`.
5. What is the difference between checked and unchecked exceptions?
6. Compare Abstract Classes and Interfaces.
7. `ArrayList` vs. `LinkedList`
8. `HashMap` vs. `Hashtable`
9. How does Garbage Collection work?
10. Method Overloading vs. Overriding
11. `String` vs. `StringBuilder` vs. `StringBuffer`
12. Is Java pass-by-value or pass-by-reference?

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