Java Masterclass GCOEN

Transcript

2. HI, I’M ANMOLDEEP! Just a curious dev on his adventure to explore the universe with bits (quite literally) I travel through space time with my Pals - Salesforce, Python, PHP, and NodeJS Salesforce Developer | AI Generalist | System Design Learner Let’s Connect https://www.linkedin.com/in/eduanmoldeep/
4. 3.5 Hour Workshop Java Masterclass Syntax to Architecture Moving beyond syntax: Deep Internals, Modern Patterns, and Production-Grade Spring Boot.
5. Module 1 The Art of Abstraction & Design
6. The Interface Contract Think of an Interface as a standard wall socket. The house wiring doesn't care what you plug in, as long as it fits the socket. The Wall Socket Interface): Defines the shape and voltage The Contract). The Device Implementation): A lamp, a laptop, or a vacuum can plug in The Implementation).
7. Coupling: The Silent Killer Tight Coupling Bad If you want to switch to a LinkedList for performance later, you have to rewrite the Service code. Loose Coupling Good You can swap new ArrayList() with new LinkedList() or new Vector() without breaking the rest of the code. public class // Hard dependency on ArrayList private new public class // Coding to the Interface private new
8. Deep Dive: Why Abstraction? Swapability Easily switch database implementations MySQL to MongoDB) if your Service only talks to a generic Repository interface. Testability Interfaces allow you to inject "Mock" objects during testing. You can't mock a tightly coupled new object easily. Maintainability Changes in the implementation details don't ripple out and break other parts of the system.
9. Module 2 Core Java Internals
10. Memory Layout: Lists ArrayList Array Backed) Contiguous memory block. Fast access O1, slow resizing. LinkedList Node Backed) Scattered memory with pointers. Slow access O(n), fast insertion.
11. The Contract Why do HashSets sometimes contain duplicates? Because you broke the contract. • Rule 1 If a.equals(b) is true, then a.hashCode() MUST be equal to b.hashCode(). • Rule 2 If hashCodes are different, the objects are definitely different. • The Bug: If you override equals but not hashCode, your object gets lost in the HashMap buckets.
12. Exceptions: The Debate Checked Exceptions // Must be caught or declared Use Case: Recoverable errors. "The file is missing, ask user for a new path." Pros: Forces developers to handle failure. Cons: Can clutter code Boilerplate). Unchecked Runtime) // Silent failure unless caught Use Case: Logic errors. "NullPointerException", "IndexOutOfBounds". Modern Trend: Spring and modern frameworks prefer Unchecked exceptions to keep code clean.
13. Pattern: Try-With-Resources The Old Way Risky The Modern Way Safe Works with any class implementing AutoCloseable. new "path" try // usage finally if null // What if close() throws? // Auto-closes even if error occurs try new "path" // usage
14. Break Time Take 30 minutes to recharge. We resume with Streams & Spring.
15. Module 3 Functional Programming & Streams
16. The Pipeline Visualization Don't think of "loops". Think of a factory assembly line. 1. Source: The raw materials List, Set). 2. Intermediate Ops: The machines Filter, Map, Sort). These are lazy. Nothing happens until... 3 . Terminal Op: The packaging Collect, Count, ForEach). This triggers the flow.
17. Code Evolution Imperative How Declarative What Reads like a sentence. "Filter active users, map to names, collect to list." new for if
18. Deep Dive: map() vs flatMap() map() One-to-One Transformation. User, User] → String, String] Input: Stream Output: Stream flatMap() One-to-Many Flattening). A, B, C → A, B, C Use Case: You have a List of Orders, and each Order has a List of Items. You want one big stream of all Items.
19. The End of NullPointerExceptions Optional is a container object which may or may not contain a non-null value. // Old Way if null return return "Unknown" // Optional Way return "Unknown"
20. Module 4 Production-Grade Spring Boot Architecture
21. Separation of Concerns This separation allows you to change the database without touching the Controller, or change the API format without touching the Database. • Controller: Handling HTTP Req/Res). NO business logic here. • Service: The Brains. Transactional business logic. • Repository: Data Access. Talking to DB.
22. Pattern: DTO Data Transfer Object) The Problem Exposing your Database Entity (e.g., User with password field) directly to the API consumer is a security risk and creates tight coupling. The Solution Create a separate POJO (e.g., UserDTO) that contains only the fields you want to show. DTO Entit y
23. Deep Implementation: ControllerAdvice Avoid Try-Catch in Controllers Don't clutter every controller method with try-catch blocks. Use AOP Aspect Oriented Programming) to handle errors globally. @RestControllerAdvice public class @ExceptionHandler public return "Not Found"
24. DI Best Practices Field Injection Autowired private Service s; Avoid. Hides dependencies, hard to test NullPointer in unit tests). Setter Injection Okay. Good for optional dependencies, but allows mutable state. Constructor Injection Best. Ensures object is fully initialized. Easy to pass Mocks in tests.
25. Mission Accomplished We've bridged the gap from Syntax to Architecture. Q & A Session