When Subagents Aren't Enough: Claude Code Agent Teams
Agent Teams, where multiple Claude Code instances divide tasks and exchange messages. Most of the time, subagents suffice, but there are moments when you need...
Claude Code Subagents: How Is Work Divided and Processed?
Why does Claude Code spin up subagents instead of doing everything alone? What are the roles of the three built-in agents, and how do you...
Beyond Prompts and Context: Harness Engineering for AI Agents
Let's look at the concept of harness engineering, why it emerged, and how it differs from prompt engineering and context engineering.
I Only Compressed CLI Output, Yet Tokens Dropped by 80%?
Just by prepending 'rtk' to a command, the agent's token consumption was reduced by 80%. We explore the operational mechanics of the open-source CLI proxy...
Why Did OpenClaw Suddenly Become a Hot Topic? (feat. Agent Runtime)
What is OpenClaw, which has captured the attention of developers in a short period of time?
Five Critical Risks of Powerful AI That Anthropic's CEO Warns About: Reading 《The Adolescence of Technology》
How can powerful AI destabilize society? This post reviews the five critical risks Dario Amodei identifies in 《The Adolescence of Technology》.
Building Custom AI Agents with the Claude Agent SDK
We examine the structure and core APIs of the Claude Agent SDK, exploring how to control agents with custom tools and hooks.
Cursor vs Claude Code: How to Choose the Right AI Coding Tool
Cursor is an IDE. Claude Code is a terminal agent. Same model, different results. Here is why.
AI Agent Skills: How to Create and Use Them
Isolate recurring rules and procedures into reusable skills. Learn the structure and authoring points of Agent Skills.
Claude Code Settings Files: How to Separate Shared Rules from Private Configuration
From permission blocking to environment variable management, learn how to build safe execution boundaries by separating team security rules from personal local settings.
Why You Should Run /init First in Claude Code
Running /init first in Claude Code anchors project context in CLAUDE.md, eliminating repeated explanations and inconsistent first responses across sessions.
JDK 25 LTS Release Notes: Key Changes at a Glance
Let’s review the key changes in JDK 25, the fifth LTS Java release, based on the official release notes.
How to Manage Claude Code Context and Reduce Token Usage
Longer sessions slow down due to the context window. Learn how to manage token usage with /compact, /clear, and /cost.
Context Engineering: The Next Step After Prompt Engineering
Explains context engineering, why it emerged, and how it differs from prompt engineering.
How to Connect MCP Servers to Claude Code and What to Watch For
With MCP, Claude Code can work with external systems as well. This post explains how to connect an MCP server.
Building an LLM API with Spring AI
Walk through Spring AI's ChatClient and ChatModel abstractions, dependency setup, LLM integration, and a simple chat API from start to finish.
How to Install Claude Code and Run It for the First Time
Install Claude Code, Anthropic's terminal-based agentic coding tool, and walk through the first run.
What Is Vibe Coding?
Andrej Karpathy coined the term vibe coding, a programming style where you describe what you want in plain English and let AI write the code....
Kotlin Scope Functions Compared: let, run, with, apply, also
Compares receiver reference style and return values of let, run, with, apply, and also with practical examples, and outlines criteria for choosing the right function....
Kotlin Error Handling and Coroutine-Based Failure Resilience
Covers exception classification, coroutine timeout, retry design, unit testing, runCatching, and lazy patterns for Kotlin failure handling.
Kotlin Coroutines: Concepts and Practical Usage
Covers coroutine fundamentals, CoroutineScope, Dispatcher, async/await, structured concurrency, and Flow. A concise guide to Kotlin coroutines for production use.
Kotlin Null Safety and Functional Programming
Covers Kotlin null safety operators and functional patterns for safer, concise code.
Kotlin Class Design and Type System Usage
A concise guide to building safe domain models using constructor validation, access control, interfaces, sealed class, generics, delegation by, and enum/value class.
Kotlin Basics: Syntax and Core Concepts
Introduces Kotlin syntax, variables, functions, control flow, and collections with practical examples.
Spring Boot 2 to 3 Migration Checklist: Breaking Changes You Must Address
Upgrading to Spring Boot 3 breaks your build immediately. Here are the compile-time breaking changes and how to fix each one.
The Optimistic Future Dario Amodei Described in 《Machines of Loving Grace》
What are the main ideas in Dario Amodei's 《Machines of Loving Grace》? And what does the optimistic future he describes actually look like?
How Spring @Transactional Works Under the Hood
From the proxy-based mechanism of Spring @Transactional to the self-invocation trap, propagation behavior, rollback rules, and readOnly optimization.
Gradle Build Performance Tuning: From 5 Minutes Down to 2
Find Gradle build bottlenecks with Build Scan, then cut build time in half using parallel execution and caching strategies.
Managing Dependencies in One Place with Gradle Version Catalog
Covers the TOML structure of Gradle Version Catalog, type-safe accessor usage, and migration strategies for existing projects.
What Is a Java Record and When Should You Use It?
A practical guide to Java records: how they work under the hood, their constraints, and when to choose them over regular classes for DTOs and...
Four Decisions to Make Before Adding a Cache Layer to Redis
Adding Redis as a cache does make things faster. The real question is which pattern to use and what to evict when memory fills up....
Why Redis Is Fast and How to Use Each Data Structure
Everyone knows Redis is fast, but when should you reach for Hash, List, Set, or Sorted Set instead of plain String?
The Proxy Pattern Hidden Behind @Transactional
How does Spring's @Transactional manage transactions before and after method execution? The secret lies in the Proxy pattern!
Kafka Connect: Monitoring and Incident Response
Where do you start when a Connector falls into FAILED state?
Kafka Connect: Building a Debezium CDC Pipeline
Moving beyond JDBC polling, this post walks through building a real-time CDC pipeline that streams MySQL change events to Kafka with Debezium and indexes them...
Kafka Connect: Introduction and Architecture
Instead of writing producers and consumers from scratch, Kafka Connect lets you build data pipelines with a single configuration. How does it work?
Tree of Thoughts and RAG in Prompt Engineering
Explains Tree of Thoughts and Retrieval-Augmented Generation and when to apply each approach.
Prompt Engineering Techniques
Summarizes practical prompt engineering techniques with implementation-oriented examples.
Prompt Engineering Basics and LLM Settings
Covers core prompt engineering concepts and practical LLM parameter settings for stable output quality.
Differences Between HTTP/1.1 and HTTP/2
HTTP/2 addresses the structural bottlenecks of HTTP/1.1 with binary framing, multiplexing, and header compression. Here is a breakdown of the key differences.
Spring RestClient Usage and Differences from RestTemplate
A practical guide to RestClient in Spring Framework 6.1, covering synchronous HTTP configuration, error handling, testing, and how it compares to RestTemplate.
Optimizing Java Images with Dockerfile Best Practices
How to reduce Java application image size and build time using Dockerfile best practices.
Java 21 LTS Is Here: What Changed?
What has changed in Java 21 LTS?
Decorator Pattern: Combining Features Without Inheritance
The Decorator pattern dynamically adds features to objects without inheritance. How far can you wrap an object?
Why Does a Kafka Consumer Keep Falling Behind?
When lag grows and rebalancing repeats, what is actually happening inside the consumer? This post follows the flow of poll and fetch.
Kafka Message Keys: Is It Really Enough to Just Put One In?
One message key changes ordering guarantees, parallelism, and even hot partitions.
Kafka Exactly-Once: Is It Really Processed Only Once?
Examines the differences and limits of at-most-once, at-least-once, and exactly-once, and organizes where duplicates and data loss occur in Kafka.
Kafka Producer: How Safe and How Fast?
Walks through the Kafka producer send path, acks settings, batching and compression, the idempotent producer, and transactions with code.
Kafka Streams Error Handling and Recovery Strategies
Covers the handler architecture that processes deserialization, production, and business-logic errors in Kafka Streams, along with State Store recovery strategies.
Docker Compose Operational Patterns and Environment-Specific Configuration Strategy
Frequently used Docker Compose patterns and operational cautions from a production perspective.
Building a Local Environment with the Docker Compose Specification
How to build a consistent local backend environment based on the Docker Compose Specification.
Kafka Streams Windows and Joins
Covers how Tumbling, Hopping, and Session windows work, along with KStream-KStream time-based joins, Grace Period, and State Store retention management.
What Is Docker Compose?
What Docker Compose is, why it matters, and how to use it in local development.
Kafka Streams KStream and KTable
Organizes why KStream and KTable interpret the same topic differently, and explains stateless and stateful operations, KStream-KTable joins, and Serdes configuration through code.
Kafka Streams Concepts and Architecture
Compares direct Consumer/Producer API composition with Kafka Streams and explains core architectural concepts such as Topology, Task, and State Store through code.
Kafka Consumer Offsets and Commit Strategies
Covers the internal structure of the __consumer_offsets topic, compares automatic and manual commit strategies, and reviews offset reset scenarios and consumer lag monitoring.
Kafka Error Handling and Dead Letter Topic Design
Covers Spring Kafka's error handler architecture, the internal behavior of ErrorHandlingDeserializer and DeadLetterPublishingRecoverer, and DLT topic design and replay strategies.
What Is Kafka Schema Registry and Why Does It Matter?
What Kafka Schema Registry is, why teams need it, and what to check in production adoption.
Why Kafka Consumer Rebalancing Happens
A production-focused guide to Kafka consumer rebalancing: causes, deployment lag spikes, duplicate processing, and scale-out checkpoints.
How Many Kafka Partitions Do You Need? Why More Consumers Do Not Always Increase Throughput
How to size Kafka partitions: throughput targets, ordering guarantees, and scaling pitfalls in production.
Kafka Topic Configuration Reference
A practical guide to frequently used Kafka topic configurations (retention, cleanup policy, replication, and message size) with examples.
Java Sealed Class vs Abstract Class vs Interface: When to Use Each
Compares sealed class, abstract class, and interface in Java with practical criteria and examples.
Kafka Consumer Reprocessing Strategies
A code-focused guide to common Kafka consumer reprocessing patterns and how to choose among them.
ChatGPT: Can AI Replace Developers?
The AI chatbot released by OpenAI. What is ChatGPT?
Fixing gem Permission Errors (Gem::FilePermissionError)
How to resolve Gem::FilePermissionError when running Ruby's gem package manager
Adapter Pattern: The Solution for Incompatible Interfaces
When the interface of an external library does not match your system, the Adapter pattern connects the two without modifying existing code.
Auto-Create Spring Batch Metadata Tables
How to configure automatic creation of metadata tables used by Spring Batch
How to Generate Random Numbers in Java and What to Watch
What options exist for random number generation in Java, and what caveats should you know?
Turn Off the Charging Chime on MacBook
Remove the notification sound that plays when you connect a charger to a MacBook
Set Default Values in Spring @Value Annotation
What default values can you use with Spring's @Value annotation, and how do you configure them?
How to Read MySQL EXPLAIN Query Plans
A practical guide to reading MySQL EXPLAIN output and identifying the fields that actually matter for query tuning.
What Is Spring Cloud OpenFeign and What Should You Watch Out For
What is Spring Cloud OpenFeign, and what do you need to know before adopting it? A practical walkthrough covering synchronous calls, timeouts, retries, and more....
FileNotFoundException When Running as a JAR
Cases where FileNotFoundException occurs when running a Java application as a JAR
Why MySQL Joins and ORDER BY Get Slow
MySQL joins and ORDER BY slow down because of intermediate result size, filesort overhead, OFFSET paging, and aggregation queries.
Fix xcrun: invalid active developer path After a macOS Upgrade
How to fix the "xcrun: error: invalid active developer path" error after upgrading macOS
Why Is My MySQL Query Slow Even With an Index?
Composite index ordering, function application, type casting, and covering indexes all determine whether MySQL actually benefits from your index.
Where to Start When Analyzing MySQL Slow Queries
Beyond execution time, what else matters in a MySQL slow query? Call frequency, rows examined, sorting, and aggregation all deserve a closer look.
Fixing JUnit5 @DisplayName Not Working in IntelliJ
How to fix cases where IntelliJ IDEA does not display labels declared with JUnit5 @DisplayName
Profiling Applications in IntelliJ
What profiling tools are available in IntelliJ IDEA Ultimate?
Simplify Object Mapping with MapStruct
Use MapStruct to simplify object mapping between DTOs and Entities (feat. Spring Boot, Lombok)
Java ThreadLocal: Usage and Caveats
What ThreadLocal is in Java, how to use it, and what to watch out for in real applications.
What Is New in Java 17: First LTS Release in 3 Years
A new Java LTS release after 3 years. What features were added in JDK 17?
git push Error: Please use a personal access token instead
If you see "Support for password authentication was removed on August 13, 2021. Please use a personal access token instead" while pushing to GitHub, how...
What If a Spring Data JPA Field Name Matches a Database Reserved Word?
How to handle syntax errors when JPA entity class/field names match database reserved words such as order or group
Managing SQL When Using Spring JDBC
Spring JDBC is simple to configure and has a low learning curve, but SQL gets mixed into business logic and hurts readability. How can we...
Template Method Pattern: Fixing the Skeleton, Changing the Steps
Fixing the overall flow while changing specific steps is the core of the Template Method pattern. Spring's JdbcTemplate also relies on this principle.
Java effectively final
What is "effectively final" in Java, where a variable is not declared final but behaves as final because its reference is not changed after initialization?...
Java BigDecimal: Accurate Real Numbers and Floating Point
How can Java represent real numbers accurately, and what is floating-point representation?
Java Optional: 5. A Closer Look at Optional
How can you use Optional in ways that align with its intent?
Java Optional: 4. Terminal Optional Methods
How to end Optional chaining and extract values or handle branches conditionally
Java Optional: 3. Intermediate Optional Methods
How to filter or transform values in Optional objects
Java Optional: 2. Introduction to Optional
What is the Optional class added in Java 8?
Java Optional: 1. What Is null?
What is null in Java, and why does it cause so much pain?
Java BigInteger: Representing Very Large Integers
How can Java represent very large integers?
Spring Cloud Config: Changes in Spring Boot 2.4
Spring Cloud Config-related changes introduced in Spring Boot 2.4
Querydsl: Avoid JPA N+1 with fetch join
Use Querydsl fetchJoin to avoid the N+1 problem in JPA
What Are Coupling and Cohesion?
Why should we design for low coupling and high cohesion?
Querydsl: Introduction and Usage
What is Querydsl, why do we need it, and how do we use it?
How to Avoid Storing _class Field in MongoDB from Spring Boot
How to configure Spring Boot so MongoDB documents do not store the _class field
Encryption and Decryption in Java
How to implement encryption and decryption in Java, including algorithm, mode of operation, and padding basics.
MyBatis Error: Invalid bound statement (not found)
What if 'Invalid bound statement (not found)' occurs when executing a MyBatis query?
Can Spring Register and Use Multiple DataSources?
Let's register multiple DataSources with Spring AbstractRoutingDataSource and switch them by context.
Code With Me: Pair Programming with IntelliJ IDEA
Let's look at the 'Code With Me' feature that supports collaborative development and pair programming in IntelliJ IDEA.
RestTemplate and WebClient
RestTemplate is expected to be deprecated. Use WebClient.
Cryptographic Techniques: Substitution, Transposition, Block Ciphers, and Stream Ciphers
What types of cryptographic techniques exist? Let's look at substitution and transposition ciphers, and block and stream ciphers.
How to Use the chmod Command on Linux
Learn about the chmod command for changing file and directory permissions on Linux.
How to Measure Code Execution Time in Java
How can you measure how long code takes to execute in Java?
Symbolic Link
What is a symbolic link, a special kind of file that contains a reference to a file or directory in Linux?
Design Your GitHub Profile
Design your GitHub profile with README.md
How to Fix a Node.js Project Not Being Recognized in IntelliJ
How to resolve the "Unresolved function or method for require()" warning when developing a Node.js project with IntelliJ IDEA/WebStorm
How to Get the auto_increment Key Value After Insert in MyBatis
How to get the auto_increment key value of inserted data after executing an insert query in MyBatis
How to Run Code When a Spring Boot Application Starts
Is there a way to run specific code when a Spring Boot application starts?
What’s New in Java 14?
A practical overview of new features and notable changes introduced in JDK 14.
Builder Pattern for Many Parameters
As the number of parameters in a constructor increases, the code becomes difficult to read. How does the Builder pattern solve this problem?
Resolving DataBufferLimitException in Spring WebClient
How to resolve DataBufferLimitException when WebClient exceeds the default codec memory buffer limit.
Java Scripting API: Migrating to GraalVM
Let's replace Nashorn script engine, deprecated in Java 11, with GraalVM.
What Is the crossdomain.xml File?
Let's look at crossdomain.xml, the security policy file required for Flash (SWF) to access data from external domains.
Java Scripting API: Bindings, ScriptContext, and Execution Performance
Execute JavaScript from Java, manage state with bindings and ScriptContext, and improve execution performance.
Java Scripting API: Calling JavaScript Functions from Java
Use the Java Scripting API to invoke functions defined in a JavaScript file from Java.
JSON Schema: Implementing a Validator in Java
Let's implement a JSON Schema validator in Java code.
JSON Schema: Combining Schemas, Conditional Schemas, and Reuse
How to combine JSON schemas, apply conditional logic, and reuse repeated schema fragments.
What Is RSS? RSS 2.0 Specification and Format
What is RSS (Rich Site Summary, Really Simple Syndication)? Let's look at RSS 2.0 specification and format.
JSON Schema: Basic Schema Definitions and Validation
Validate JSON data with JSON Schema using fundamental schema declaration and validation patterns.
JSON Schema: What Is JSON Schema?
Is there a way to validate JSON data? Like XSD for XML, how can you validate JSON?
Spring Cloud Config: Auto Refresh with Git Webhook
Use a Git webhook to refresh Spring Cloud Config automatically whenever configuration changes.
Comparing Performance: String vs StringBuilder vs StringBuffer in Java
What are the differences between String, StringBuilder, and StringBuffer in Java, and which one performs fastest?
Spring Cloud Config: Spring Cloud Bus Example
Do we have to call every client whenever Spring Cloud Config changes? Connect all clients with Spring Cloud Bus.
Spring Cloud Config: Introduction and Example
How can you refresh Spring configuration changes without rebuild and redeploy, and externalize configuration files?
Add Comments to a Jekyll Blog with utterances
Add a comment system to a Jekyll blog by using utterances, which is backed by GitHub issues
Can Spring Include Package Names in Bean Identifiers?
Can classes with the same name in different packages be registered as Spring beans? How can package names be included in bean names?
Why Constructor Injection Is Preferred Over Field Injection with @Autowired
Why is constructor injection generally recommended over field injection with @Autowired?
How to Fix ClassNotFoundException: JAXBException When Running a Spring Boot Project on Java 9
You upgraded to Java 9 and now your Spring Boot project fails at startup. How do you fix it?
Stack Overflow, Growth and Experience Points for Developers
Growth and experience points you can gain from the Stack Overflow community that most developers have visited at least once
[Effective Java 3rd Edition] Item 11. Always Override hashCode When You Override equals
[Effective Java 3rd Edition] Item 11. Always override hashCode when you override equals
[Effective Java 3rd Edition] Item 76. Strive for Failure Atomicity
[Effective Java 3rd Edition] Item 76. Strive for failure atomicity
[Effective Java 3rd Edition] Item 23. Prefer Class Hierarchies to Tagged Classes
[Effective Java 3rd Edition] Item 23. Prefer class hierarchies to tagged classes
[Effective Java 3rd Edition] Item 24. Favor Static Member Classes over Nonstatic
[Effective Java 3rd Edition] Item 24. Favor static member classes over nonstatic
[Effective Java 3rd Edition] Item 15. Minimize the Accessibility of Classes and Members
[Effective Java 3rd Edition] Item 15. Minimize the accessibility of classes and members
[Effective Java 3rd Edition] Item 86. Implement Serializable with Great Caution
[Effective Java 3rd Edition] Item 86. Implement Serializable with great caution
[Effective Java 3rd Edition] Item 89. For Instance Control, Prefer Enum Types to readResolve
[Effective Java 3rd Edition] Item 89. For instance control, prefer enum types to readResolve
[Effective Java 3rd Edition] Item 90. Consider Serialization Proxies Instead of Serialized Instances
[Effective Java 3rd Edition] Item 90. Consider serialization proxies instead of serialized instances
[Effective Java 3rd Edition] Item 88. Write readObject Methods Defensively
[Effective Java 3rd Edition] Item 88. Write readObject methods defensively
[Effective Java 3rd Edition] Item 87. Consider Using a Custom Serialized Form
[Effective Java 3rd Edition] Item 85. Consider using a custom serialized form
[Effective Java 3rd Edition] Item 85. Prefer Alternatives to Java Serialization
[Effective Java 3rd Edition] Item 85. Prefer alternatives to Java serialization
[Effective Java 3rd Edition] Chapter 12. Serialization
[Effective Java 3rd Edition] Chapter12: Serialization
[Effective Java 3rd Edition] Item 81. Prefer Concurrency Utilities to wait and notify
[Effective Java 3rd Edition] Item 81. Prefer concurrency utilities to wait and notify
[Effective Java 3rd Edition] Item 80. Prefer Executors, Tasks, and Streams to Threads
[Effective Java 3rd Edition] Item 80. Prefer executors, tasks, and streams to threads
[Effective Java 3rd Edition] Item 79. Avoid Excessive Synchronization
[Effective Java 3rd Edition] Item 79. Avoid excessive synchronization
[Effective Java 3rd Edition] Chapter 11. Concurrency
[Effective Java 3rd Edition] Chapter11: Concurrency
[Effective Java 3rd Edition] Item 78. Synchronize Access to Shared Mutable Data
[Effective Java 3rd Edition] Item 78. Synchronize access to shared mutable data
[Effective Java 3rd Edition] Chapter 10. Exceptions
[Effective Java 3rd Edition] Chapter 10: Exceptions
[Effective Java 3rd Edition] Item 68. Adhere to Generally Accepted Naming Conventions
[Effective Java 3rd Edition] Item 68. Adhere to generally accepted naming conventions
[Effective Java 3rd Edition] Item 62. Avoid Strings Where Other Types Are More Appropriate
[Effective Java 3rd Edition] Item 62. Avoid strings where other types are more appropriate
Factory Method Pattern: Delegating Object Creation to Subclasses
What are the benefits of delegating object creation to subclasses? We examine the structure of the Factory Method pattern and its practical use cases in...
[Effective Java 3rd Edition] Chapter 9. General Programming
[Effective Java 3rd Edition] Chapter9: General Programming
What Is the Difference Between #{} and ${} in MyBatis?
When writing SQL in MyBatis XML mappers, what is the difference between #{} and ${}?
[Effective Java 3rd Edition] Chapter 8. Methods
[Effective Java 3rd Edition] Chapter8: Methods
Java Serialization: readResolve and writeReplace
What roles do readResolve and writeReplace play in Java serialization?
[Effective Java 3rd Edition] Item 44. Favor the Use of Standard Functional Interfaces
[Effective Java 3rd Edition] Item 44. Favor the use of standard functional interfaces
Java Serialization: writeObject and readObject
What roles do writeObject and readObject play in Java serialization, and why are they private?
[Effective Java 3rd Edition] Chapter 7. Lambdas and Streams
[Effective Java 3rd Edition] Chapter7: Lambdas and Streams
[Effective Java 3rd Edition] Item 39. Prefer Annotations to Naming Patterns
[Effective Java 3rd Edition] Item 39. Prefer annotations to naming patterns
[Effective Java 3rd Edition] Chapter 6. Enums and Annotations
Effective Java 3rd Edition Chapter 6: Enums and Annotations
[Effective Java 3rd Edition] Chapter 5. Generics
Effective Java 3rd Edition Chapter 5: Generics
[Effective Java 3rd Edition] Chapter 4. Classes and Interfaces
[Effective Java 3th Edition] Chapter4: Classes and Interfaces
Sorting a MySQL VARCHAR Column as a Number
How do you sort a VARCHAR column as a number in MySQL? Convert the string to a number and order it.
Handling JSONP in Spring Boot and Solving CORS Issues
How do you implement JSONP responses in Spring Boot, and how do you solve cross-domain issues?
[Effective Java 3rd Edition] Chapter 3. Methods Common to All Objects
[Effective Java 3th Edition] Chapter3: Methods Common to All Objects
The Difference Between map and flatMap in Java
What is the difference between map and flatMap in Java 8?
Squash Commits with git rebase
How do you combine multiple commits into one? Use git rebase to clean up commit history.
Java Serialization: What to Consider and Why It Is Discouraged
What should you watch out for when using Java serialization, and why is it discouraged?
Building an IntelliJ Plugin: 3. Build & Publish
Build your IntelliJ plugin and publish it to the JetBrains plugin repository.
Building an IntelliJ Plugin: 2. Define an Action
Define an Action to run an IntelliJ plugin
Building an IntelliJ Plugin: 1. Environment Setup
Build a plugin for IntelliJ IDEA from scratch
Why Do We Need Vuex?
What is Vuex, and why does a Vue app need it?
Manage Multiple Java Versions with jEnv
Install jEnv on macOS and manage multiple JDK versions.
Fixing IntelliJ Error: source release 8 requires target release 1.8
Fix the IntelliJ error: Error:java: javacTask: source release 8 requires target release 1.8.
Detect JAXB Parsing Errors with ValidationEventHandler
Detect JAXB unmarshal errors and find the error line with ValidationEventHandler.
JAXB Marshalling and Unmarshalling
Use JAXB (Java Architecture for XML Binding) to marshal and unmarshal XML in Java.
FTP Active vs Passive Mode
What is the difference between FTP active and passive modes?
Java Exceptions: Checked vs Unchecked
How does Java classify exceptions? Differences between checked and unchecked exceptions.
Java Licensing? OpenJDK vs Oracle JDK
Oracle's Java licensing changes and the differences between OpenJDK and Oracle JDK.
[Effective Java 3rd Edition] Chapter 2. Creating and Destroying Objects
[Effective Java 3rd Edition] Chapter 2. Creating and Destroying Objects
Java Streams: 5. Common Mistakes
Common pitfalls and trade-offs when using the Java Stream API.
Java Streams: 4. Examples
Practical examples using the Java Stream API.
Setting Up a Spring MVC + Maven Project in IntelliJ
Create a Maven-based Spring MVC project in IntelliJ IDEA.
Java Streams: 3. Terminal Operations
What terminal operations exist in Java streams, and how do you use them?
Java Streams: 2. Intermediate Operations
What intermediate operations exist in Java streams, and how do you use them?
Java Streams: 1. API Overview and Stream Creation
What are Java 8 streams? This post introduces the Stream API and ways to create streams.
[Effective Java 3rd Edition] Item 17. Minimize Mutability
[Effective Java 3rd Edition] Item 17. Minimize mutability
The final Keyword in Java
What does the final keyword mean in Java, and how should you use it?
[Effective Java 3rd Edition] Item 82. Document Thread Safety
[Effective Java 3rd Edition] Item 82. Document thread safety
[Effective Java 3rd Edition] Item 74. Document All Exceptions Thrown by Each Method
[Effective Java 3rd Edition] Item 74. Document all exceptions thrown by each method
Numeric Literals and Underscores in Java
Since Java 7, you can use underscores in numeric literals to improve readability.
[Effective Java 3rd Edition] Item 66. Use Native Methods Judiciously
[Effective Java 3rd Edition] Item 66. Use native methods judiciously
How to Autowire a Static Field
Inject a bean into a static field in the Spring Framework.
[Effective Java 3rd Edition] Item 58. Prefer for-each Loops to Traditional for Loops
[Effective Java 3rd Edition] Item 58. Prefer for-each loops to traditional for loops
[Effective Java 3rd Edition] Item 8. Avoid Finalizers and Cleaners
[Effective Java 3rd Edition] Item 8. Avoid finalizers and cleaners
Multiple Tomcat Instances
How do you run multiple Tomcat instances?
[Effective Java 3rd Edition] Item 31. Use Bounded Wildcards to Increase API Flexibility
[Effective Java 3rd Edition] Item 31. Use bounded wildcards to increase API flexibility
[Effective Java 3rd Edition] Item 50. Make Defensive Copies When Needed
[Effective Java 3rd Edition] Item 50. Make defensive copies when needed
Installing Node.js on macOS and Running an Example
Install Node.js on Mac OSX and run a Hello World example.
Getting Started with Node.js
What is Node.js and what makes it different? A concise introduction.
Java Serialization: What Is SerialVersionUID?
What is SerialVersionUID, and how does it affect Java serialization?
Java Serialization: What Is Serialization?
What are serialization and deserialization in Java, and how do you use them?
[Effective Java 3rd Edition] Item 42. Prefer Lambdas to Anonymous Classes
[Effective Java 3rd Edition] Item 42. Prefer lambdas to anonymous classes
Benefits of Java Generics and Pitfalls to Avoid
Why are Java generics useful, and what should you watch out for?
[Effective Java 3rd Edition] Item 4. Enforce Noninstantiability with a Private Constructor
[Effective Java 3rd Edition] Item 4. Enforce noninstantiability with a private constructor
Java Generics
A practical overview of Java generics, including generic classes, interfaces, and methods.
Java 8 Date and Time
Use Java 8 date/time classes (LocalDate, LocalDateTime) to handle dates and times.
Why Java Date and Calendar Are a Bad Fit
Why should you avoid Java’s legacy Date and Calendar APIs?
[Effective Java 3rd Edition] Item 28. Prefer Lists to Arrays
[Effective Java 3rd Edition] Item 28. Prefer lists to arrays
Differences Between var, let, and const
Explore the differences between var, let, and const introduced in ECMAScript 2015 (ES6).
[Effective Java 3rd Edition] Item 34. Use Enums Instead of Int Constants
[Effective Java 3rd Edition] Item 34. Use enums instead of int constants
Server-Side Rendering vs Client-Side Rendering
What is the difference between server-side rendering (SSR) and client-side rendering (CSR)?
Python switch Statements
How do you implement a switch statement in Python?
[Effective Java 3rd Edition] Item 18. Favor Composition over Inheritance
[Effective Java 3rd Edition] Item 18. Favor composition over inheritance
[Effective Java 3rd Edition] Item 26. Don't Use Raw Types
[Effective Java 3rd Edition] Item 26. Don't use raw types
[Effective Java 3rd Edition] Item 10. Obey the general contract when overriding equals
[Effective Java 3th Edition] Item 10. Obey the general contract when overriding equals
Python URL Parsing and Calling (urllib)
urllib library that makes URL parsing and calling easy in Python
Entering Korean Comments in Python (SyntaxError: Non-ASCII character)
Let's learn about methods for entering comments in Korean in Python.
[Effective Java 3rd Edition] Item 2. Consider a builder when faced with many constructor parameters
[Effective Java 3rd Edition] Item 2. Consider a builder when faced with many constructor parameters
Python if __name__ == "__main__" Meaning
What is the meaning of the if __name__ == "__main__" declaration in Python?
Argument and Parameter
What's the difference between function arguments and parameters?
Docker: Following Docker Installation and Commands
Docker, an open-source virtualization platform based on containers! Let's just do it!
log4j, logback, and log4j2
Let's learn about log4j, logback, and log4j2, Java's logging frameworks.
Java Kafka Producer and Consumer configs Settings
Let's set configs for Kafka Producer and Kafka Consumer.
Java Kafka Producer and Consumer Example Implementation
Implementing Kafka Producer and Kafka Consumer using Java.
Installing Jekyll on Windows 10 and Creating GitHub Blog
Let's install Jekyll in Windows 10 environment and create a github blog
Cron Expressions
Let's learn about Cron Expressions used in Cron Scheduler
Gradle Project Structure and Gradle Wrapper
Let's learn about the structure of Gradle-based projects and Gradle Wrapper that enables builds even without Gradle installation.
What is Gradle?
Let's learn about Gradle, a build tool based on Groovy that focuses on build automation and development support
Java Upcasting and Downcasting
What are Upcasting and Downcasting in Java?
Setting Up Log4j2 in Spring Boot
Let's set up Log4j2 for logging in Spring Boot projects
Setting Up Spring Boot Project in IntelliJ
Let's create a Spring Boot project using IntelliJ IDE
grep Examples and Options
Let's find specific strings in files with the grep command
Java and Behavior Parameterization
Passing code to methods when execution behavior hasn't been decided yet.
Change Git Commit Author (Changing Commit Author)
I mistakenly entered the commit author and even pushed it. Can I change the commit author's name again?
Difference Between Process and Thread
What differences do processes and threads have?
Naver Interview Review (SW Development, Phone Interview, Technical Interview)
Naver SW Development Interview Review
NHN Technology Services Written Test Review (SW Development, NTS pretest)
NHN Technology Services Written Test Review
Software Maestro Interview Review (Group Discussion Evaluation, Coding Test)
Software Maestro (SW Maestro) Interview Review
Spring Bean Lifecycle Methods and Execution Order
What are the Bean Lifecycle methods in Spring Framework? And in what order are they executed?
Com2us Interview Review (Platform Development)
Com2us Platform Development Interview Review
Korea Electric Power Corporation Interview Review (IT Information & Communication)
Korea Electric Power Corporation IT (Information & Communication) Interview Review
Java Method Overriding and Overloading
What's the difference between Method Overriding and Method Overloading in Java?
LINE Plus Interview Review (SW Development, Technical Interview)
LINE Plus SW Development Interview Review
LeetCode 344. Reverse String
Output the input string in reverse
Lotte Data Communication Company Spectacle Audition Review
Review of the no-spec hiring process of Lotte Data Communication Company, an IT company of the Lotte Group
Java String Objects and String Literals
There are two ways to declare strings in Java. What's the difference between String and new String()?
Binary Search Tree: Implementation in Java
A Java implementation of a Binary Search Tree.
Binary Search Tree: Theory and Introduction
Tree, a hierarchical structure similar to trees, combines with binary search. What is a Binary Search Tree?
Observer Pattern
When an object's state changes, is there a way for other objects that depend on it to know?
Java Collection Synchronization
Synchronization is important. What I intended can appear differently to others. Learning about synchronization when using collections
LeetCode 2. Add Two Numbers
Find the result of adding two lists consisting of positive numbers by each index
LeetCode 3. Longest Substring Without Repeating Characters
Find the longest substring without repeating characters in a given string
Java References and Garbage Collection
Following Garbage Collection, learning about object references of Java references.
Spring Framework Summary: Testing
Testing is one of the most effective methods for learning Spring.
Java Garbage Collection
Learning about Garbage, which refers to memory no longer in use, and Garbage Collection, which cleans it up.
Functional Programming and Object-Oriented Programming
Functional Programming and Object-Oriented Programming
Spring Framework Summary: Inversion of Control
Learning about Spring's Inversion of Control (IOC, Inversion of Control)
Why Are Computers Based on Binary System?
Learning why computers use the binary system.
Spring Framework Summary: Design Patterns
Studying Spring Framework and design patterns!
Java String replaceAll Method $(Dollar Sign) Issue
Issues you may encounter when using String replaceAll method in Java
Strategy Pattern
A pattern that encapsulates object behavior into classes to dynamically and freely change them
Finding Prime Numbers Quickly Using Sieve of Eratosthenes
Finding prime numbers quickly using the Sieve of Eratosthenes!
Singleton Pattern
Learning about the singleton pattern that limits the number of objects. And why is the singleton pattern called an anti-pattern?
Java Interface
What is an interface in Java? And how can multiple inheritance be implemented in Java?
Java Reflection and Dynamic Loading
Dynamically load (Dynamic Load) other classes within a class.
Resolving Jekyll Execution Error on MacOS High Sierra
Resolving Jekyll execution errors in High Sierra version.
Resolving MySQL Root Password Change Error on Mac OS
Resolving access denied for user... error
Levenshtein Distance Algorithm (Edit Distance Algorithm)
Examining the edit distance algorithm for finding similarity between strings.
OSI 7 Layer
Open System Interconnection 7 Layer
Time Complexity and Space Complexity
Learning about complexity for evaluating algorithm performance.
The this Keyword in Java
Learning about the this keyword that refers to the object itself in Java
TCP vs UDP Differences and TCP/IP
Learning about the differences between TCP and UDP.
Java File Compression and Decompression (ZipInputStream, ZipOutputStream)
Java file compression and decompression using java.util.zip package
Creating Java Executable Files
Creating Java executable files using JSmooth.
Abstract Classes and Methods in Java
What's the reason for using abstract classes and abstract methods in Java?
Java Access Modifiers
What access modifiers are there in Java? What's the difference between public, protected, private, and default access modifiers?
Java Inheritance
Examining the concept and usage examples of inheritance in Java
Why Does Java Main Method Use public static?
Why is the structure of the main method in Java public static void main(String[] args)?
NTFS, FAT32, and exFAT Formats
Differences in Windows file systems
LeetCode 412. Fizz Buzz
Output Fizz for multiples of 3, Buzz for multiples of 5, and FizzBuzz for both from numbers 1 to N
LeetCode 292. Nim Game
Nim game, which can also be said to be the origin of Baskin-Robbins game
Big Endian and Little Endian
What's the difference between Big Endian and Little Endian? Learning about methods of arranging bytes.
scp and rsync (Secure Copy & Remote Synchronization)
Transferring files to or from a remote host! What's the difference between scp and rsync?
LeetCode 1. Two Sum
Given an array containing 1~N, find the indices of the array that can make the input number M
Resolving Maven Tomcat 404 Error
Finding various causes of 404 errors in Maven + Tomcat.
Selection Sort
Learning about selection sort, one of the in-place sorting algorithms.
Quick Sort
Learning about the quick sort algorithm based on divide & conquer.
Merge Sort
Learning about the merge sort algorithm that goes through divide, conquer, and combine processes.
Connecting Apache and Tomcat (apache, tomcat, mod_jk)
Connecting web server Apache and WAS Tomcat through modjk. And why do we connect Apache and Tomcat?
jQuery Sortable (Implementing Sorting with Drag and Drop)
Implementing drag & drop sorting with jQuery UI!
Java Finalize Method
How to release memory-allocated objects in Java?
Java Swing LookAndFeel
Customize Swing UI with LookAndFeel.
Java Data Types
What data types does Java provide?
Java Language Characteristics
Java is object-oriented and platform independent, and it supports multithreading and encapsulation. What else defines the language?
Bracket Matching with a Stack (Java)
How can you verify matching brackets in an expression? Use a stack to validate pairs.