Summary of "Top 20+ Java 8 Interview Questions & Answers [Most Important] | JavaTechie"

Summary of the Video: "Top 20+ Java 8 Interview Questions & Answers [Most Important] | JavaTechie"

The video provides an extensive overview of important Java 8 interview questions and answers, focusing on key features introduced in Java 8, such as Functional Interfaces, Lambda Expressions, and the Stream API. The speaker emphasizes the necessity of understanding these concepts thoroughly for Java developer interviews.

Main Ideas and Concepts:

Java 8 Features:
- Functional Interfaces: An interface with only one abstract method. Examples include Runnable, Callable, and Comparator.
- Lambda Expressions: A concise way to represent a method of a functional interface.
- Stream API: A new abstraction for processing sequences of elements (like collections) in a functional style.
Functional Interface Explanation:
- Definition: Contains one abstract method, can have multiple default and static methods.
- Examples: Function, Predicate, Consumer, Supplier.
Lambda Expression:
- Simplifies the syntax for implementing Functional Interfaces.
- Can be used to create instances of Functional Interfaces without boilerplate code.
Stream API:
- Enables functional-style operations on streams of elements.
- Supports operations like filtering, mapping, and reducing.
- Distinction between map (for single field extraction) and flatMap (for one-to-many relationships).
CompletableFuture:
- An enhancement over the Future interface that allows for asynchronous programming.
- Supports chaining and combining multiple tasks.
Threading Concepts:
- Differences between single-threaded (stream) and multi-threaded (parallel stream) processing.
- Use of wait and notify for thread coordination.

Methodology and Instructions:

Functional Interface Creation:
- Define an interface with one abstract method.
- Use the @FunctionalInterface annotation (optional but recommended).
Writing Lambda Expressions:
- Remove the method signature prefix and data types.
- Define the body of the method using concise syntax.
Using Stream API:
- Convert collections to streams using .stream().
- Chain methods like filter(), map(), collect(), etc.
- Use Collectors for grouping and counting.
CompletableFuture Usage:
- Use CompletableFuture.runAsync() for asynchronous execution.
- Handle results and exceptions in a non-blocking way.

Key Interview Questions Covered:

What features do you know about Java 8?
Explain Functional Interfaces and provide examples.
What is a lambda expression, and how is it used?
What is the Stream API, and how does it work?
What are the advantages of using CompletableFuture over Future?
How do you decide the thread pool size?

Speakers or Sources Featured:

The primary speaker is identified as JavaTechie, who presents the content in a tutorial format.

This summary encapsulates the key points and methodologies discussed in the video, providing a comprehensive overview for anyone preparing for Java 8 interviews.

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