[CS Technical Interview 6] Java and Object-Oriented Programming that gets you talking

A course where you understand the core concepts of Java and Object-Oriented Programming (OOP), and even train to explain them verbally in interviews.

(4.9) 22 reviews

548 learners

Level Basic

Course period Unlimited

Java
Java
oop
oop
Tech Interview
Tech Interview
Java
Java
oop
oop
Tech Interview
Tech Interview

Reviews from Early Learners

4.9

5.0

pray

100% enrolled

Wow... this is really so good...;;;; I need to save up money and buy everything in the roadmap.. I'm curious if you're planning to do any Spring lectures too.. I'll buy it right away..

5.0

karabiner

100% enrolled

The lecture pinpointed the key points, making it highly efficient for the time invested.

5.0

박상완 Sang Wan

55% enrolled

While preparing for Java developer interviews, I needed a systematically organized lecture, and this course was a great help. The detailed explanations of JVM structure, memory areas, exception handling, and other theories are memorable. This is a core summary lecture that can be directly applied in actual interviews.

What you will gain after the course

  • Java, Understanding Core Object-Oriented Concepts

  • The ability to explain verbally in technical interviews

  • Practical Workbook PDF to Prepare for Follow-up Questions

🥲 Have you ever had an experience like this in an interview?

1. Giving an answer while confusing concepts

Interviewer What are the characteristics of object-oriented programming?
💬 Candidate It's the SOLID principles. First, S is......(omitted)...

This is a situation where the characteristics of object-oriented programming (abstraction, encapsulation, inheritance, polymorphism) and
the object-oriented design principles (SOLID) have been confused.
This can give the impression that the framework of basic concepts has not been established.

2. Knowing only the "What," but failing to explain the "How" or "Why"

Interviewer: What are the characteristics of TCP?
💬 Candidate: It is a protocol that guarantees reliability.
Interviewer: What are the mechanisms that guarantee reliability?
💬 Candidate: Uh... well... it's like... making sure it's transmitted safely... that kind of...

This is a state where you only know the superficial definition and are not prepared to explain the principles.
If the 3-way handshake, sequence numbers, ACK, retransmission, flow control, and congestion control
are not connected into a single coherent flow, you will inevitably get stuck on follow-up questions.

3. When you get tongue-tied on basic questions

Interviewer: What is HTTP?
💬 Candidate: Uh… it’s for sending and receiving data on the web… something like that…?

It's a very familiar concept, but when you actually try to explain it in a single sentence, the words don't come out.
This isn't a lack of knowledge, but a lack of experience in organizing and speaking it out loud.


Knowing it is not enough. It only becomes a true skill when you can explain it in words.

🔥 So, this is how it's structured.

Next-level, premium content for interview preparation

1⃣ CS notes organized based on interview preparation

  • Concepts and principles that must be checked before an interview are gathered together and provided as lecture materials.

  • It is structured so that you can fill in the basics while also being able to take it out and review it right up until the interview.

  • It is not just a simple summary, but includes diagrams and easy explanations so that even non-majors can fully understand it.


Computer Architecture Lecture Material Example

2⃣ Appendix | Interview Practice Materials Provided

  • In an interview, the ability to explain clearly is much more important than simply knowing the information.

  • However, organizing and practicing on your own is a difficult and tedious task.

  • At the end of the lecture materials, we have included "answering in one or two sentences" training to save you the trouble of organizing it yourself.


Example of Database Lecture Appendix

3⃣ Preparing for follow-up questions Technical Interview Practical Workbook PDFprovided

  • "Will this lecture alone really be enough for speaking practice?"
    After much deliberation over this question,

    I have created a practical technical interview workbook.

  • It is designed so that you can practice speaking just like a real interview on your own.

  • You can find detailed information about the workbook's structure and how to use it in the workbook introduction video at the beginning of the lecture.

Operating System Workbook Example

4⃣ CS learning app for reviewing anytime, anywhere

To ensure you don't forget the core concepts learned in the lecture,
we provide a dedicated mobile learning app..

You can naturally review by repeatedly studying quizzes and core concepts during your commute or even during short breaks
.

💡 How to make the most of this abundant content

1⃣ Download the materials and learn the core concepts while listening to the lectures.
2⃣ Take your own notes on the important parts to create your own CS interview notes.
3⃣ Save them on your phone and review them briefly whenever you have a spare moment.

If you have an interview coming up and
are short on time → Quickly sharpen your interview instincts with the Appendix [Interview Practice] in the lecture materials.
If you have time → Complete your speaking practice like a real interview using the Technical Interview Practical Workbook and Mobile App..

🎯 Recommended for the following people

Non-majors, job seekers, career changers, etc., who are preparing for technical interviews and need to be able to explain CS fundamentals verbally

CS majors who need to review and reorganize

I have studied it before, but
I don't even know where to start organizing all that CS knowledge again

Don't open those thick textbooks
again.
We will clearly summarize only the core concepts.

Non-majors who feel overwhelmed by CS

I'm preparing for a technical interview for the
first time, and I'm at a loss
as to where to start

By following the roadmap,
you can focus on learning
only the core CS concepts.

Job seekers looking to change careers with limited time

Forget that, I don't have time.
I need to

quickly summarize only the CS topics that appear in interviews.

There are lecture materials and interview chapters that allow for
quick review
even on your own.

🔥 Reviews from students who experienced it first

A truly helpful lecture.
Already proven by 5,000+ students.

⭐️⭐️⭐️⭐️⭐️

1. A lecture where you can see how much the author has thought and agonized from the student's perspective (it seems the flow of the learner's understanding was taken into account)
2. Understanding is easy due to the variety of visual materials and examples
3. When learning new knowledge, previously learned content is mentioned and recalled to connect the information. As the knowledge connects, a big picture is formed.
4. The depth of knowledge is not shallow. I am taking the Operating Systems course right after Computer Architecture, and the synergy is great.
5. It perfectly scratches the itch of wondering "why" & "why we use it."
ps. I feel sorry for the author, but.. it's a lecture I want to keep all to myself.

- 'Operating Systems' Course Review

⭐️⭐️⭐️⭐️⭐️

Even with the short lecture time, I love how you clearly explain only the important parts. Since it's mostly a theoretical lecture, I didn't expect you to cover SQL queries, but it was great that you showed examples and taught basic syntax and how to write queries one by one. After that, the sections on joins, normalization, transactions, indexes, data optimization, and security were excellent. Although I haven't taken other paid courses yet, the last lecture appendix titled "Interview Practice" provided actual questions and answers, making it great for self-study and practice. The lecture time isn't long if you stay focused, so I think I'll go through it a few more times. Thank you.

-'Database' Course Review

⭐️⭐️⭐️⭐️⭐️

The core content was explained clearly and with a logical flow, which helped me quickly organize my understanding of data structures. Thank you for the great lecture.

- 'Data Structures' Course Review

⭐️⭐️⭐️⭐️⭐️

Wow... this is seriously so good...;;;; I need to save up and buy the whole roadmap.. I'm curious if you have any plans to teach Spring as well.. I'll buy it immediately..

-'Java and Object-Orientation' Course Review

⭐️⭐️⭐️⭐️⭐️

This is a lecture where you can set aside about a day to organize the key concepts of JavaScript all at once! It's great for a quick reminder before an interview👍



- 'JavaScript' Course Review

⭐️⭐️⭐️⭐️⭐️

As a non-CS major, I was worried about how to study CS knowledge, especially computer architecture and operating systems. However, the content was divided into appropriate amounts, making it easy to learn without feeling overwhelmed, and it was great because it felt like getting private tutoring from an expert. I plan to take the operating systems lecture as well, and I'm looking forward to it. Thank you!

- 'Computer Architecture' Course Review

🖐 Hello! Let me introduce myself! 🙇

As a non-major, I initially focused solely on algorithms and coding tests while preparing for my first job as a developer.
I gained a fair amount of confidence and passed most coding tests, but I repeatedly failed at the next hurdle: the technical interview. What was the problem? It was the lack of CS (Computer Science) knowledge.

I understand the thirst for fundamental skills (CS knowledge, programming languages, etc.) better than anyone. I built up my own know-how by digging through countless materials on my own, and eventually, after graduating from Seoul National University, I am working as a 🧑🏻‍💻 Kakao Developer.

Since I was young, I have been more confident than anyone else in combining and restructuring various materials to create my own "consolidated notes." This lecture is the secret notebook that contains all that know-how and passion.

🚀 The sixth subject of the CS Series for Fluent Speaking is Java & OOP.

  • JVM and Garbage Collection (GC)—you might know the concepts, but can you explain how they actually work?

  • Have you heard of multithreading and synchronization, but find it difficult to answer in just a sentence or two during an interview?

📖 Curriculum packed with only the essentials gói gọn những nội dung cốt lõi

This is the curriculum and key keywords you will learn in this course.

If there are any unfamiliar keywords, take this opportunity to master them once and for all.

  1. Object-Oriented Basics

    • Characteristics of Object-Oriented Programming, SOLID principles, etc.

  2. Java Overview

    • Java features, JVM / Garbage Collector (GC), reference types, Call by Value, static keyword, etc.

  3. Object-Oriented Programming

    • Java's OOP, polymorphism, interfaces and abstract classes, etc.

  4. Collections

    • Characteristics and various comparisons of List, Set, and Map

    • Comparison of various Sets (HashSet, LinkedHashSet, TreeSet)

    • Comparison of various Maps (HashMap, LinkedHashMap, TreeMap, ConcurrentHashMap)

  5. Multi-threading and Concurrency

    • Methods for implementing multi-threading

    • •synchronized keyword and volatile keyword, etc.

  6. Exception Handling and Other Concepts

    • Exception handling methods, exception hierarchy, serialization/deserialization, comparison of String and StringBuilder/StringBuffer, etc.

  7. Modern Java (Post-Java 8)

    • Functional interfaces and lambda expressions, comparison between collections and streams

  8. [Appendix] Interview Practice

    • Reviewing key concepts once more in a Q&A format

✏ Here is what we will cover

1⃣ Object-Oriented Design Principles and Application Methods

  • Learn everything from the core philosophy of object-oriented programming, SRP (Single Responsibility Principle), to the five SOLID principles.

  • By comparing poorly designed code with refactored code, you will understand how to improve maintainability and scalability.

  • Through practical Java code examples, you can clearly learn the 'application method' rather than just theory.

SRP explanation and code examples

2⃣ Easy explanation of confusing core Java concepts using diagrams

  • JVM and Memory Structure Explains the JVM execution process and the roles of Stack/Heap memory areas easily through diagrams.

  • GC (Garbage Collector) Operating Principles You can firmly grasp the concepts by learning the complex GC process through visual diagrams rather than abstract explanations.

  • You will learn in depth, along with diagrams, how the call by value method is reflected in actual memory states and code execution. phản ánh vào trạng thái bộ nhớ thực tế và việc thực thi mã nguồn thông qua các sơ đồ minh họa.

Example of GC operation process

Example of explaining JVM components

Explanation of the call by value principle

3⃣Multi-threading and Synchronization Strategies for Immediate Practical Use

  • Various thread creation methods implemented with Thread, Runnable, and ExecutorService

  • synchronized, volatile keyword meanings and operational differences

  • Compare code execution results before and after synchronization, and learn how to access shared resources safely.

Example explanation of the synchronized keyword

👀 Lecture Preview

If the video is frozen, please refresh the page :)

Explanation of Garbage Collector (GC)

All in One! A complete summary of essential and confusing Java concepts

Notes before taking the course

  • Learning material format provided: PDF

  • Prior knowledge of basic Java syntax is required.

Recommended for
these people

Who is this course right for?

  • A non-major who feels overwhelmed because it's their first time studying CS

  • Computer science students who need to organize CS concepts before a technical interview

  • Job seekers who are short on time ahead of a technical interview

Need to know before starting?

  • JAVA Basic Syntax

  • Learning becomes much easier if you have a grasp of basic operating system concepts like memory and threads.

Hello
This is yiyj10305235

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Learners

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Answers

4.9

Rating

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Courses

Education and Experience

  • Graduate of Seoul National University

  • Current Kakao Server Developer

    Course Introduction I am creating the "Fluent CS" series to help you articulate CS concepts during interviews. Course Philosophy Having started development as a non-computer science major, I understand the importance of CS...

Course Introduction I am creating the "CS for Speaking" series to help you articulate CS concepts during interviews. Course Philosophy Having started development as a non-computer science major, I...

Course Introduction

I am creating the
CS Speaking series to help you articulate CS concepts during interviews.

Teaching Philosophy

I started my development career as a non-CS major and went through a lot of trial and error while personally organizing everything from CS fundamentals to technical interviews. Based on the learning methods and conceptual organization know-how accumulated through that process, I create content that makes core concepts encountered in practice and interviews easy to understand through illustrations.
"I am creating the lectures that I needed back then."

Blog yiyj1030.tistory.com → Running a tech blog that simplifies CS, algorithms, and practical concepts. Contact yiyj1030@gmail.com

Blog

  • yiyj1030.tistory.com
    → Running a tech blog that simplifies and organizes CS, algorithms, and practical concepts

Contact

yiyj1030@gmail.com

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Curriculum

All

40 lectures ∙ (3hr 6min)

Course Materials:

Lecture resources
Published: 
Last updated: 

Reviews

All

22 reviews

4.9

22 reviews

  • doitdoit님의 프로필 이미지
    doitdoit

    Reviews 31

    Average Rating 5.0

    5

    100% enrolled

    This is a lecture you can watch to grasp the major topics before an interview.

    • yiyj10305235
      Instructor

      Thank you for the course review. I hope this lecture isn't the end and that we can continue the learning journey together. I look forward to seeing you again in the next series :)

  • asd21123님의 프로필 이미지
    asd21123

    Reviews 11

    Average Rating 4.5

    5

    100% enrolled

    Wow... this is really so good...;;;; I need to save up money and buy everything in the roadmap.. I'm curious if you're planning to do any Spring lectures too.. I'll buy it right away..

    • tommy0419님의 프로필 이미지
      tommy0419

      Reviews 24

      Average Rating 5.0

      5

      100% enrolled

      I took this course to quickly review concepts. Overall, you covered everything well, which helped me review quickly. Thank you.

      • hungrylosemuscle님의 프로필 이미지
        hungrylosemuscle

        Reviews 24

        Average Rating 5.0

        5

        100% enrolled

        It's great for quickly organizing the overall concepts!

        • happhuy2089님의 프로필 이미지
          happhuy2089

          Reviews 1

          Average Rating 5.0

          5

          100% enrolled

          It felt like it meticulously filled in the missing parts. I think other series would also be helpful to watch before interviews.

          • yiyj10305235
            Instructor

            Thank you for the course review. I hope this lecture isn't the end and that we can continue the learning journey together. I look forward to seeing you again in the next series :)

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