🗺️ Mind Map & Slides
Poora Core Java ek nazar mein — mind map se connections dekho, phir slides mein har topic ka quick recap.
Core Java ☕
Basics 📦
Variables
Loops
Arrays
Type Casting
Methods
OOP 🏠
Class & Object
Inheritance
Polymorphism
Enums
Generics
Collections 🧺
List
Set
Map
Comparator
Exceptions 🥅
try-catch
throw
Multi-catch
Multithreading 🏃
Thread
Executor
Deadlock
Strings 🪨
immutable
StringBuilder
Java 8+ 🌊
Lambda
Streams
Optional
File I/O 📁
FileReader
try-with-resources
Memory & Lifecycle 🧹
Stack vs Heap
Garbage Collection
Serialization
📽️ Infographic Slides
☕Introduction
Java Kya Hai?
- Java = programming language (1995 se)
- Write Once, Run Anywhere
- Code -> Compiler -> Bytecode -> JVM -> Run
📦Storing Data
Variables & Data Types
- Variable = labeled box for data
- Types: int, double, char, boolean, String
- Java statically typed hai
➕Doing Math & Comparisons
Operators
- + - * / % maths ke liye
- % remainder deta hai
- == > < compare, && || logic jodte hain
🚦Control Flow
if-else (Decision Making)
- if chalta hai jab condition true ho
- else chalta hai jab false ho
- else if se multiple checks
🔁Repeating Work
Loops (for, while)
- for: jab count pehle se pata ho
- while: jab tak condition true ho
- do-while: kam se kam 1 baar chalta hai
🗄️A Row of Boxes
Arrays
- Fixed-size row of same-type values
- Index 0 se start hota hai
- array[i] se value access hoti hai
🏠Blueprint vs Real Thing
Class & Object
- Class = blueprint
- Object = real instance
- new keyword se object banta hai
🐣Object ka Janam
Constructor
- Class-jaisa special method
- new hote hi auto-call hota hai
- Initial values set karta hai
🔗Self vs Shared
this & static keyword
- this = apna current object
- static = class ke saath shared
- Object ke bina bhi ClassName.member
🌳Parent → Child
Inheritance
- extends se parent ke features milte hain
- Code reuse badhta hai
- Child apni nayi cheezein bhi add karta hai
🎭Many Forms
Polymorphism
- Ek naam, kayi roop
- Overloading = same class, diff parameters
- Overriding = child redefines parent method
💊Protecting Data
Encapsulation
- Fields ko private rakho
- getter/setter se controlled access
- Galat change hone se bachata hai
🚗Hiding Complexity
Abstraction
- Complexity chhupao, essentials dikhao
- abstract class / interface se define hota hai
- "kya" batao, "kaise" implementer decide kare
📜Contract vs Partial House
Interface vs Abstract Class
- Interface = 100% contract, multiple allowed
- Abstract class = partial, sirf ek allowed
- Java 8+ interface mein default methods bhi
🥅Catching Errors
Exception Handling
- try = risky code
- catch = error ko pakadta hai
- finally = hamesha chalta hai
🧺Storing Groups of Data
Collections: List, Set, Map
- List = ordered, duplicates OK
- Set = sirf unique values
- Map = key-value pairs
🏃♂️Doing Many Things at Once
Multithreading
- Thread = independent execution path
- Parallel kaam ek saath hota hai
- synchronized se data safe rehta hai
🪨Immutable Text
String Handling
- String immutable hai
- Change par naya object banta hai
- StringBuilder mutable & fast hota hai
🔄Converting Types
Type Casting & Wrapper Classes
- Widening: automatic, chhota->bada
- Narrowing: manual, bada->chhota, data loss possible
- Autoboxing/Unboxing: primitive <-> wrapper
🧩Reusable Blocks of Code
Methods & Recursion
- Method = reusable code block
- Pass by value — copy milti hai
- Recursion = method khud ko call karta hai
🔀More Control Flow
switch, break & continue
- switch = vending machine ek value ke liye
- break = loop/switch turant rok do
- continue = is round ko skip karo
🧮Grid of Boxes
2D Arrays
- 2D array = array of arrays
- grid[row][col] se access
- Matrix/grid data ke liye best
🪪Every Object's Built-in Toolkit
Object Class: equals, hashCode, toString
- Har object ko Object class se milte hain
- toString() readable text ke liye override karo
- equals()+hashCode() saath override karo
🪆Class Inside a Class
Nested & Inner Classes
- Static nested = independent helper class
- Inner = outer object se juda
- Anonymous = naam-less, one-time use
🎨A Fixed Set of Choices
Enums
- Fixed set of named constants
- Type-safe — galat value allowed nahi
- Traffic-signal jaisa: sirf predefined options
🧰Type-Safe Reusable Code
Generics
- <T> se ek hi class kayi types ke liye kaam karti hai
- Compile-time type safety milti hai
- List<String>, Box<Integer> jaise examples
🚪Who Can See What
Access Modifiers & Packages
- public/private/protected/default = 4 levels
- Package = related classes ka group
- Encapsulation ke liye access control zaroori
📊Comparator, Queue & TreeMap
Advanced Collections
- Comparable = class ka apna order (compareTo)
- Comparator = custom order (compare)
- Queue = FIFO, TreeMap = auto-sorted keys
🌊Writing Less, Doing More
Java 8+: Lambda & Streams
- Lambda = chhoti inline function
- Functional Interface = ek hi abstract method
- Stream = filter->map->collect chain
📁Reading & Writing Files
File Handling / Java I/O
- FileReader/Writer = characters padhna/likhna
- BufferedReader = fast line-by-line reading
- try-with-resources = auto-close
🧯Multi-catch & Custom Hierarchy
Advanced Exception Handling
- catch (A | B e) = multi-catch
- Custom exceptions apna hierarchy bana sakte hain
- Bade projects mein errors organize karta hai
⚙️Thread Lifecycle & Executors
Advanced Multithreading
- Thread lifecycle: New->Runnable->Running->Waiting->Terminated
- ExecutorService = thread pool manager
- Deadlock = do threads hamesha ke liye atak jaate hain
🧹How Java Cleans Up
Memory Management & Garbage Collection
- Stack = method calls, fast, auto-clean
- Heap = objects, GC yaha kaam karta hai
- GC = automatic memory cleanup
🧬Object Lifecycle Extras
Init Blocks, Cloning & Serialization
- static block = class load par ek baar
- clone() = object ki copy
- Serializable = object ko save/bhejo, wapas banao