Lambda Expressions 🚀

Mentor's Note: Lambda expressions (introduced in Java 8) are the biggest change in Java's history. They allow you to write 10 lines of code in just 1 line. It's like switching from a typewriter to a modern laptop! 💡

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🌟 The Scenario: The Delivery Order 📝

Imagine you are ordering food.

• The Old Way (Anonymous Class): You have to sign a long paper contract, write your full name, address, and date, just to say "I want Pizza." 📦
• The New Way (Lambda): You just send a text: Me -> Pizza. 📦
• The Result: You get your food faster with less effort. The -> (Arrow) is your message from you to the action. ✅

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📖 Concept Explanation

1. What is a Lambda?

A lambda expression is a short block of code which takes in parameters and returns a value. It is essentially an Anonymous Method (a method without a name).

2. Syntax

(parameter1, parameter2) -> { code block }

• Parameters: The input. 📥
• Arrow ->: Connects input to the logic.
• Body: What to do with the input. ⚙️

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🎨 Visual Logic: The Shrink Ray ⚡

graph LR
    A["Before: <br/>public void run() { <br/> System.out.println('Hi'); <br/>}"] -- Shrink Ray! --> B["After: <br/>() -> System.out.println('Hi')"]
    style B fill:#dfd,stroke:#333

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💻 Implementation: The Lambda Lab

Java (Modern)With Conditions

import java.util.ArrayList;

public class Main {
    public static void main(String[] args) {
        ArrayList<Integer> numbers = new ArrayList<>();
        numbers.add(5);
        numbers.add(9);
        numbers.add(8);

        // 🛒 Scenario: Print each item
        // 🚀 Action: Using a Lambda inside forEach
        numbers.forEach( (n) -> { System.out.println("Processing: " + n); } );

        // 🛍️ Outcome: Clean, readable code without manual loops.
    }
}

// 🚀 Action: Find items matching a condition
numbers.removeIf(n -> n % 2 == 0); // Remove all even numbers! ✂️

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📊 Sample Dry Run

List	Lambda Logic	Result
[5, 10, 15]	n -> n > 8	[10, 15]
["Hi", "Bye"]	s -> s.length()	[2, 3]

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📈 Technical Analysis

• Functional Interfaces: Lambdas only work with interfaces that have Exactly One abstract method (e.g., Runnable, Comparator).
• Target Type: Java automatically guesses the data type of the lambda based on the context! 🧠

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🎯 Practice Lab 🧪

Task: The Custom Greeter

Task: Given a list of names, use forEach and a Lambda to print "Hello, [Name]!" for every person in the list. Hint: names.forEach(name -> ...);. 💡

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💡 Interview Tip 👔

"Interviewers love asking: 'Why use Lambdas?' Answer: They enable Functional Programming in Java, make code more concise, and are essential for using the Java Streams API efficiently!"

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💡 Pro Tip: "One interface, multiple implementations—that's the power of being flexible!" - Anonymous

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