Java: Novice to Pro Guide

1. Novice Level (Foundations)

1.1 Introduction

• What is Java? Object-Oriented, Platform Independent (WORA - Write Once, Run Anywhere).
• JVM, JRE, JDK: Understanding the differences.
• Setup: Installing JDK, IntelliJ IDEA/Eclipse.

1.2 Basic Syntax

• public static void main(String[] args)
• Variables & Data Types: primitives (int, double, boolean, char) vs wrappers (Integer, Double)
• Operators: Arithmetic, Relational, Logical, Assignment.

1.3 Control Flow

• if-else, switch
• Loops: for, enhanced for, while, do-while
• break, continue

1.4 arrays & Strings

• Arrays: Declaration, initialization, iterating.
• Strings: Immutable nature, String Pool, StringBuilder/StringBuffer.

2. Intermediate Level (OOP & Core Libraries)

2.1 Object-Oriented Programming

• Classes & Objects: Fields, Methods.
• Constructors: Default, Parameterized.
• Inheritance: extends, super, this.
• Polymorphism: Overloading vs Overriding.
• Encapsulation: Access Modifiers (private, protected, public, default).
• Abstraction: Abstract Classes vs Interfaces.

2.2 Exception Handling

• try-catch-finally block.
• Checked vs Unchecked Exceptions.
• throw vs throws.
• Custom Exceptions.

2.3 Collections Framework

• List: ArrayList, LinkedList.
• Set: HashSet, TreeSet, LinkedHashSet.
• Map: HashMap, TreeMap, LinkedHashMap.
• Queue: PriorityQueue.
• Collections utility class.

2.4 Generics

• Type safety.
• Generic Classes and Methods.
• Wildcards (?).

3. Advanced Level (Enterprise Ready)

3.1 Java 8+ Features

• Lambdas: Functional programming syntax.
• Streams API: filter, map, reduce, collect for collection processing.
• Optional Class: Handling nulls gracefully.
• Functional Interfaces: Predicate, Function, Consumer, Supplier.

3.2 Multithreading & Concurrency

• Thread class vs Runnable interface.
• Synchronization (synchronized keyword/blocks).
• java.util.concurrent: ExecutorService, Callable, Future, CountDownLatch.

3.3 File I/O & NIO

• FileReader/FileWriter, BufferedReader.
• NIO (New I/O): Channels, Buffers, Selectors, Files class.

3.4 JDBC (Database Connectivity)

• Driver Manager, Connection, Statement, ResultSet.
• PreparedStatement (preventing SQL Injection).
• Connection Pooling concepts.

4. Expert Level (Architecture & Tuning)

4.1 Memory Management & Garbage Collection

• Heap vs Stack memory.
• Garbage Compilation algorithms (G1, ZGC).
• Memory Leaks analysis.

4.2 Design Patterns

• Creational: Singleton, Factory, Builder.
• Structural: Adapter, Decorator, Proxy.
• Behavioral: Observer, Strategy, Template Method.

4.3 Spring Framework (Brief Overview)

• Dependency Injection (IoC).
• Spring Boot Basics.
• Annotations (@Component, @Autowired, @RestController).

4.4 JVM Tuning & Performance

• Profiling tools (JVisualVM, JProfiler).
• JIT Compilation.
• Classloaders.