# 📚 Java Programming Language – Part 9/10: Collections Framework
#Java #Collections #DataStructures #Programming

Welcome to Part 9 of our Java series! Today we'll explore the powerful Collections Framework - essential for handling groups of objects efficiently.

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## 🔹 Collections Framework Overview
The Java Collections Framework provides:
- Interfaces (List, Set, Map, etc.)
- Implementations (ArrayList, HashSet, HashMap, etc.)
- Algorithms (Searching, Sorting, Shuffling)


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## 🔹 Core Interfaces
| Interface | Description | Key Implementations |
|-----------|-------------|---------------------|
| List | Ordered collection (allows duplicates) | ArrayList, LinkedList |
| Set | Unique elements (no duplicates) | HashSet, TreeSet |
| Queue | FIFO ordering | LinkedList, PriorityQueue |
| Map | Key-value pairs | HashMap, TreeMap |

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## 🔹 List Implementations
### 1. ArrayList

List<String> names = new ArrayList<>();
names.add("Alice");
names.add("Bob");
names.add(1, "Charlie"); // Insert at index 1

System.out.println(names); // [Alice, Charlie, Bob]
System.out.println(names.get(0)); // Alice

### 2. LinkedList

List<Integer> numbers = new LinkedList<>();
numbers.add(10);
numbers.addFirst(5); // Add to beginning
numbers.addLast(20); // Add to end

System.out.println(numbers); // [5, 10, 20]

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## 🔹 Set Implementations
### 1. HashSet (Unordered)

Set<String> uniqueNames = new HashSet<>();
uniqueNames.add("Alice");
uniqueNames.add("Bob");
uniqueNames.add("Alice"); // Duplicate ignored

System.out.println(uniqueNames); // [Alice, Bob] (order may vary)

### 2. TreeSet (Sorted)

Set<Integer> sortedNumbers = new TreeSet<>();
sortedNumbers.add(5);
sortedNumbers.add(2);
sortedNumbers.add(8);

System.out.println(sortedNumbers); // [2, 5, 8]

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## 🔹 Map Implementations
### 1. HashMap

Map<String, Integer> ageMap = new HashMap<>();
ageMap.put("Alice", 25);
ageMap.put("Bob", 30);
ageMap.put("Alice", 26); // Overwrites previous value

System.out.println(ageMap.get("Alice")); // 26
System.out.println(ageMap.containsKey("Bob")); // true

### 2. TreeMap (Sorted by keys)

Map<String, String> sortedMap = new TreeMap<>();
sortedMap.put("Orange", "Fruit");
sortedMap.put("Carrot", "Vegetable");
sortedMap.put("Apple", "Fruit");

System.out.println(sortedMap); 
// {Apple=Fruit, Carrot=Vegetable, Orange=Fruit}

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## 🔹 Iterating Collections
### 1. For-Each Loop

List<String> colors = List.of("Red", "Green", "Blue");
for (String color : colors) {
    System.out.println(color);
}

### 2. Iterator

Set<Integer> numbers = new HashSet<>(Set.of(1, 2, 3));
Iterator<Integer> it = numbers.iterator();
while (it.hasNext()) {
    System.out.println(it.next());
}

### 3. forEach() Method (Java 8+)

Map<String, Integer> map = Map.of("A", 1, "B", 2);
map.forEach((key, value) -> 
    System.out.println(key + ": " + value));

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## 🔹 Collections Utility Class
Powerful static methods for collections:

List<Integer> numbers = new ArrayList<>(List.of(3, 1, 4, 1, 5));

Collections.sort(numbers); // [1, 1, 3, 4, 5]
Collections.reverse(numbers); // [5, 4, 3, 1, 1]
Collections.shuffle(numbers); // Random order
Collections.frequency(numbers, 1); // 2

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# 📚 JavaScript Tutorial - Part 3/10: Arrays, Objects & JSON
#JavaScript #WebDev #Programming #DataStructures

Welcome to Part 3 of our JavaScript series! Today we'll master arrays, objects, and JSON - essential for handling complex data.

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## 🔹 Arrays in JavaScript
Ordered collections that can hold multiple values.

### 1. Creating Arrays

// Array literal (recommended)
const fruits = ['Apple', 'Banana', 'Orange'];

// Array constructor
const numbers = new Array(1, 2, 3);

// Mixed data types
const mixed = [1, 'Hello', true, {name: 'Ali'}];

### 2. Accessing Elements

console.log(fruits[0]);  // "Apple" (0-based index)
console.log(fruits.length);  // 3

### 3. Common Array Methods
| Method | Description | Example |
|--------|-------------|---------|
| push() | Add to end | fruits.push('Mango') |
| pop() | Remove from end | fruits.pop() |
| shift() | Remove from start | fruits.shift() |
| unshift() | Add to start | fruits.unshift('Kiwi') |
| slice() | Get sub-array | fruits.slice(1, 3) |
| splice() | Add/remove items | fruits.splice(1, 0, 'Berry') |

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## 🔹 Modern Array Methods (ES6+)
Powerful functional programming tools.

### 1. forEach()

fruits.forEach(fruit => console.log(fruit));

### 2. map()

const upperFruits = fruits.map(fruit => fruit.toUpperCase());

### 3. filter()

const longFruits = fruits.filter(fruit => fruit.length > 5);

### 4. reduce()

const sum = [1, 2, 3].reduce((total, num) => total + num, 0);

### 5. find() & findIndex()

const banana = fruits.find(fruit => fruit === 'Banana');
const bananaIndex = fruits.findIndex(fruit => fruit === 'Banana');

### 6. some() & every()

const hasApple = fruits.some(fruit => fruit === 'Apple');
const allLong = fruits.every(fruit => fruit.length > 3);

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## 🔹 Objects in JavaScript
Collections of key-value pairs (properties).

### 1. Creating Objects

// Object literal (recommended)
const person = {
    name: 'Ali',
    age: 25,
    hobbies: ['reading', 'coding'],
    address: {
        city: 'Dubai',
        country: 'UAE'
    }
};

### 2. Accessing Properties

// Dot notation
console.log(person.name);  // "Ali"

// Bracket notation (useful for dynamic keys)
const key = 'age';
console.log(person[key]);  // 25

### 3. Modifying Objects

// Add property
person.job = 'Developer';

// Delete property
delete person.age;

// Check property existence
'name' in person;  // true

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## 🔹 Object Methods
### 1. Object.keys()

const keys = Object.keys(person);  // ["name", "age", ...]

### 2. Object.values()

const values = Object.values(person);

### 3. Object.entries()

for (const [key, value] of Object.entries(person)) {
    console.log(`${key}: ${value}`);
}

### 4. Object Spread (ES9+)

const newPerson = {...person, age: 26};

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## 🔹 JSON (JavaScript Object Notation)
Universal data format for APIs.

### 1. JSON ↔️ JavaScript

// Object to JSON string
const jsonStr = JSON.stringify(person);

// JSON string to object
const parsedObj = JSON.parse(jsonStr);

### 2. JSON Structure

{
    "name": "Ali",
    "age": 25,
    "isStudent": false,
    "courses": ["Math", "CS"]
}

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## 🔹 Destructuring Assignment
Unpack values from arrays/objects.

### 1. Array Destructuring

const [first, second] = fruits;
console.log(first);  // "Apple"

### 2. Object Destructuring

const {name, age} = person;
console.log(name);  // "Ali"

// With renaming
const {name: personName} = person;

### 3. Function Parameter Destructuring

function printUser({name, age}) {
    console.log(`${name} is ${age} years old`);
}

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