Kim Young-han's Java Tutorial - Your First Step into Java with Code

"A query that ran perfectly during development suddenly slows down as data accumulates." At such times, the mark of a truly skilled developer is identifying the root cause based on solid evidence rather than guesswork, and optimizing a 30-second query down to 0.1 seconds. Master the core principles of database performance—from execution plans, indexes, and optimizers to joins and sorting—using millions of rows of real-world data. Elevate your skills and become a top-tier developer capable of independently analyzing and resolving slow queries in production environments.

Solve the challenges you inevitably face in real-world design—such as common codes, category hierarchies, history tracking, soft deletes, statistics, dynamic design, and JSON utilization—with 9 core patterns. This is not just simple theory; it contains practical know-how and selection criteria for various scenarios, proven across numerous projects. Now, become a true design expert who can confidently handle any requirement that comes your way.

Learn practical core Java object-oriented concepts easily via example code.

Learn the fundamentals of SQL and databases essential for practical work. Not only developers, but also planners and data analysts can learn SQL in depth.

Learn Java generics and collection frameworks in depth with a focus on practical applications. Also learn the basics of data structures.

You will systematically learn database design through three stages—conceptual, logical, and physical—and strengthen your skills through a practical shopping mall project. Gain real-world know-how through modern design techniques and the latest trends.

Not only developers, but also planners and data analysts learn databases step-by-step, starting from the basics of SQL.

Beginners to Spring can quickly learn the entire Spring web application development process by creating examples.

Spring beginners can grasp core principles and solidify basics via examples.

This book provides an in-depth study of various intermediate-level Java features necessary for practical work, using example code.

This course provides an in-depth study of multithreading and concurrency, from basic principles to practical applications.

For those who are new to JPA or who use JPA in practice but lack basic theory, By learning the basic theory of JPA solidly, even beginners can confidently use JPA in practice.

Learn the core HTTP features essential for practical use and how to design proper HTTP APIs.

Learn the essential modern Java technologies of Lambda, Stream, and functional programming with Java, from the basics to the practical level, in depth.

This course will cover everything you need to know about Spring Boot for practical use.

With a practical example, we will design and develop a web application using Spring Boot and JPA. Through this process, you will understand how to use Spring Boot and JPA in practice.

Learn I/O, networking, reflection, and annotations in depth, from the basics to the practical level. Build a web application server (WAS) directly in Java.

You will learn the core principles and advanced technologies of Spring in depth and be able to use Spring confidently.

Develop APIs using Spring Boot and JPA. And learn how to optimize JPA's extreme performance.

You can understand all the web technologies required for web application development from the basics and complete your learning. In MVC Part 2, you can learn all the practical application techniques needed for real-world web development, building upon the core principles and structures from MVC Part 1.

Have you ever wondered "how" the many Java libraries and frameworks you use provide this functionality? In this course, learn how to manipulate various codes or objects provided by Java and take your Java skills to the next level.

If you were to ask me which programming language is most used in companies, I would say Java. Let's have fun learning Java with fun Java education.

Practical course to master Spring Boot 3 + PostgreSQL 17 + JPA + MyBatis + Spring Security all at once!

Learn the essential modern Java technologies of Lambda, Stream, and functional programming with Java, from the basics to the practical level, in depth.

This course is for those preparing for coding tests in Java. It covers the top 10 topics that are most frequently tested in coding tests. It is structured step by step from basic to intermediate problems linked to the topic, so if you follow it step by step, you will get good results.

Beginners to Spring can quickly learn the entire Spring web application development process by creating examples.

This is an introductory Java course. It's easy.

This is a basic DFS lecture that explains the way a liberal arts major and working developer studied to get a job :) We have prepared a lecture where you can learn by solving problems yourself, with minimal boring theory lectures! After taking this lecture, you will be able to solve silver level DFS problems on your own according to Baekjoon standards.

We enable you to fundamentally understand and resolve issues where Hangeul appears broken on web pages or in databases, or files contain unknown characters.

Drawing from my own experience of feeling despondent when trying to implement practical code during my first MSA transition—despite knowing the theory—I will help you grow into a developer who guarantees perfect data consistency amidst any system failure by directly rolling back daunting compensation logic through 9-step practical patterns and AI Agent coding.

This is a Unity C# scripting course for absolute beginners who are learning programming for the first time. It was created by carefully selecting the core grammar necessary for utilizing Unity scripts.

A portfolio-focused course on deploying a React frontend and Spring Boot backend directly to the AWS cloud! This course is helpful for those who want to quickly deploy frontend and backend projects for their portfolio. You will gain the necessary knowledge for deployment through short-term, step-by-step practice, covering everything from server configuration to Docker, domain connection, Nginx, and HTTPS application!

Implement a PvZ-style tower defense in Unity from scratch using C#. A practical course where even beginners can learn to build grid-based character placement, enemy pathing/blocking, and coin management.

We teach Spring Boot 3, which is the most widely used in back-end development, in a completely easy way. We create a bulletin board that is essential and most widely used in back-end development in a follow-up manner. We study with the popular book 'Jump to Spring Boot 3'.

You can systematically learn stock trading automation using Python and the Interactive Brokers API, which holds the top spot in global market share.

If you have studied basic grammar, you naturally want to try making something, right? This is a lecture designed to help beginner C++ programmers become proficient in object-oriented programming by creating simple games. We provide the 'minimum' code needed to start game programming on your own and share object-oriented know-how that cannot be mastered through grammar study alone. Have fun creating and quickly leap to an intermediate level or beyond!

Did you give up while studying Spring? Even complete beginners new to coding and non-majors can make it from JSP to Spring Boot without giving up - we'll open the path to Spring Boot for you.

An AI system that grades and reviews your code in just 5 seconds—imagination becomes reality. This course is an all-in-one project curriculum for creating a **'GitHub PR Auto-Analysis and Grading Bot'** using Spring AI. When a student submits an assignment (Pull Request), the server detects it, and the AI analyzes the code changes (Diff). The grading results are then stored in a database, feedback is automatically posted as a GitHub comment, and the student can check their results on a dedicated dashboard. From backend to AI integration and frontend (Vaadin), all with just Java! This is the ultimate introductory guide for any developer who wants to build their own AI service from A to Z.

Learn the process of application development/release/update all at once through the Android Brainwashing Classroom. Learn the basics of JAVA and learn the distribution and update process while actually building an Android app. Implement the core functions of In★Gram yourself through practice. You can get started even if you don't know programming.

💡 Even non-developers can go from startup MVP to monetized service in just 10 hours with AI! 💰 Development that used to cost tens of millions in outsourcing fees now completely solved for 120,000 won 🎯 Complete 5 real business projects including business card recognition, sentiment analysis, and location analysis 🔥 If you're a planner, marketer, or aspiring entrepreneur, implement ideas without developers ⚡ Start now and acquire lifelong development independence skills!