Explain lambda expressions in Java

💡 Concept: Lambda Expressions in Java

Lambda expressions, introduced in Java 8, provide a concise way to represent anonymous functions and enable functional programming constructs.

📘 Quick Intro

Lambda expressions simplify the syntax for implementing functional interfaces, improving readability and enabling parallel processing.

🧠 Analogy

Think of lambda expressions as shorthand instructions or recipes that you pass around without giving them a full name or class.

🔧 Technical Explanation

Syntax: (parameters) -> expression or block
They implement functional interfaces (interfaces with a single abstract method).
Enable cleaner, more concise code especially for collection processing.
Support for closures, capturing variables from the enclosing scope.
Improve opportunities for parallel and lazy evaluation in streams.

🎯 Use Cases

✅ Replacing anonymous classes for single-method interfaces.
✅ Simplifying event handling and callbacks.
✅ Enabling functional-style operations with Streams API.

💻 Code Example: Lambda Expression in Java


import java.util.Arrays;
import java.util.List;

public class LambdaExample {
    public static void main(String[] args) {
        List list = Arrays.asList("Java", "Lambda", "Expressions");
        
        list.forEach(s -> System.out.println(s.toUpperCase()));
    }
}

❓ Interview Q&A

Q1: What are lambda expressions?
A: Anonymous functions that implement functional interfaces.

Q2: When were lambda expressions introduced?
A: In Java 8.

Q3: What is a functional interface?
A: An interface with a single abstract method.

Q4: Can lambda expressions access final variables?
A: Yes, they can capture effectively final variables.

Q5: How do lambda expressions improve code readability?
A: By reducing boilerplate syntax.

Q6: Can lambda expressions throw checked exceptions?
A: Yes, if declared.

Q7: What is the syntax of a lambda expression?
A: (parameters) -> expression/block.

Q8: Are lambda expressions stateless?
A: Yes, generally stateless and immutable.

Q9: Can lambda expressions be used with streams?
A: Yes, they are commonly used.

Q10: How do lambda expressions enable parallel processing?
A: By enabling functional-style operations that streams can parallelize.

📝 MCQs

Q1. What are lambda expressions?

Named functions
Anonymous functions
Classes
Interfaces

Q2. When were lambda expressions introduced?

Java 7
Java 8
Java 9
Java 10

Q3. What is a functional interface?

Multiple abstract methods
Single abstract method
No abstract methods
None

Q4. Can lambda expressions access final variables?

No
Yes
Sometimes
Never

Q5. How do lambda expressions improve code readability?

Increase verbosity
Reduce boilerplate syntax
No effect
Complicate code

Q6. Can lambda expressions throw checked exceptions?

No
Yes
Sometimes
Never

Q7. What is the syntax of a lambda expression?

function()
-> expression
(parameters) -> expression/block
None

Q8. Are lambda expressions stateless?

No
Yes
Sometimes
Depends

Q9. Can lambda expressions be used with streams?

No
Yes
Sometimes
Never

Q10. How do lambda expressions enable parallel processing?

Disable parallelism
Enable functional-style operations
No effect
Slow down

💡 Bonus Insight

Lambda expressions provide the foundation for functional programming features in modern Java development.

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