This article explains the main Java garbage collection algorithms—Mark‑Sweep, Mark‑Copying, Mark‑Compact, and Generational Collection—detailing their principles, advantages, and drawbacks, helping developers choose the appropriate strategy for efficient memory management in backend applications.
This article walks through the LeetCode 77 "Combinations" problem, explaining the backtracking approach, presenting detailed examples, constraints, and providing complete implementations in Java, C++, and Python for generating all k‑element subsets of the range [1, n].
This article examines common pitfalls in Spring Boot controller implementations—such as excessive try‑catch blocks, inline validation, and business logic—then demonstrates cleaner alternatives using @Valid, validation annotations, and global exception handling to produce concise, maintainable controllers.
This article explains how to design and implement a flexible plugin mechanism for Java applications, covering the benefits of decoupling, common implementation strategies such as ServiceLoader (SPI), custom configuration loading, and Spring Boot integration via spring.factories, with complete code examples and a real‑world case study.
This article explains LeetCode problem 77, describing how to generate every possible combination of k numbers from the range 1 to n using backtracking, and provides complete Java, C++, and Python implementations along with a brief analysis and constraints.
This article explains how to dynamically switch between multiple service providers, such as SMS vendors, in a Spring‑based backend by using spring‑smart‑di's @AutowiredProxySPI and related annotations, covering configuration, Maven dependency, enabling the feature, and custom proxy implementations.
This article explains why force‑killing a Spring Boot process is unsafe and walks through four practical ways—using Actuator, ApplicationContext.close(), PID‑based kill commands, and SpringApplication.exit()—to achieve a graceful shutdown while preserving in‑flight tasks and releasing resources.
This tutorial demonstrates how to create an AI-driven Spring Boot application by integrating DeepSeek's large language model, covering project setup, dependency configuration, API key management, and implementing a REST controller that provides weather forecasts via a conversational interface.
This article explains the concepts, usage conditions, execution flow, internal mechanisms, and best‑practice guidelines for Java's wait() and notify() methods, illustrated with a producer‑consumer example and code snippets for safe thread coordination.
The article explains five fundamental concurrency levels—Blocking, Starvation‑Free, Obstruction‑Free, Lock‑Free, and Wait‑Free—detailing their definitions, implementation mechanisms in Java, performance trade‑offs, suitable scenarios, and practical decision guidance for building high‑performance, reliable systems.
This article explains the fundamentals of I/O in Unix and Java, covering the distinction between user and kernel space, the five Unix I/O models, the evolution from select/poll to epoll/kqueue, and how modern network frameworks like Reactor and Proactor leverage these mechanisms for high‑performance networking.
This article explains RocketMQ's message tracing feature, covering its definition, key data attributes, core benefits, configuration steps for both normal and IO‑isolated modes, the underlying implementation mechanism, supported trace topics, and provides complete Java code examples for custom TraceTopic usage and verification.
This article explains how SpringBoot’s default embedded Tomcat can be replaced with the high‑performance Undertow server, shows the necessary Maven dependencies, lists Undertow’s key features, presents benchmark results comparing QPS and memory usage, and concludes with recommendations for high‑concurrency applications while also noting related AI‑product promotions.
This article revisits Sentinel, Alibaba’s open‑source traffic‑governance component, explaining its core concepts, resource and rule definitions, step‑by‑step demos for basic and Spring integration, and a detailed walkthrough of its internal processor slots, statistics nodes, flow control, and degradation mechanisms.
This article explains the core principles of Java class loading, including the uniqueness of Class objects per ClassLoader, various loading sources such as dynamic generation, network, ZIP archives, and databases, the lifecycle stages, delegation model, isolation, and practical recommendations for safe and efficient deployment.
This article presents a continuously updated collection of over 100 Spring Boot 3 practical cases, demonstrating how to implement permission authentication using Spring AOP, custom annotations, JWT utilities, interceptors, a global exception handler, a security context, and a custom argument resolver, complete with test examples and screenshots.
This article demonstrates how to create a PDF template by first designing a Word document, converting it to PDF, inserting text, option, and image fields using a PDF editor, and then programmatically filling those fields with Java iText code, including dependency setup and image insertion.
The article explains why data desensitization is essential for enterprises, classifies common masking techniques, and provides concrete implementation guides for database, log, and output level masking in Java applications using MyBatis plugins and Fastjson filters, complete with sample code and configuration.
An extensive Spring Boot 3 case collection featuring over 100 practical examples is now available, accompanied by a detailed tutorial that demonstrates how RestTemplateAdapter and RestClientAdapter simplify HTTP request handling, improve code readability, and ensure seamless integration with third‑party APIs, with a commitment to permanent updates.
Implementing real‑time statistics in a Java performance testing engine involves adding TPS and average latency counters, creating a controllable monitoring thread, using LongAdder for high‑concurrency metrics, and gracefully shutting down the thread, enabling testers to instantly observe system load and detect bottlenecks.
The article explains how using double for monetary values can cause precision loss—turning 2.01 into 2.00—illustrates the binary representation issue, demonstrates failing code, and presents a robust solution using Java's BigDecimal with sample conversion methods and performance tests.
The article introduces DeepSeek4j 1.4, a Java Spring Boot library that overcomes existing framework limitations by preserving DeepSeek's chain‑of‑thought capabilities, adding full reactive streaming, and providing a simple one‑line API along with quick‑start instructions and code examples.
An analysis of Perforce's 2025 Java Developer Productivity Report reveals that over half of Java developers face deployment delays and tool shortages, while AI tools like ChatGPT and GitHub Copilot are increasingly adopted for code completion, refactoring, and documentation, signaling a strategic shift toward AI in Java development.
The article demonstrates how to build a dynamic Chain of Responsibility in a Spring Boot and MyBatis‑Plus application by defining an abstract handler, implementing concrete @Component beans that modify a shared Lombok‑based context, retrieving them via an ApplicationContext‑aware proxy utility, and invoking them in a client‑specified order through a REST endpoint, while suggesting LiteFlow as a production alternative.
This article introduces Spring Framework's ResponseBodyEmitter, explains its advantages over SSE for asynchronous HTTP responses, demonstrates practical usage with a real‑time log‑streaming example, outlines core methods, working principles, best‑practice considerations, and compares it with traditional Streaming and Server‑Sent Events.
This article introduces Java's Service Provider Interface (SPI), demonstrates a step‑by‑step example with multiple Maven modules, explains how to create interface and implementation classes, configure META‑INF/services files, and delves into the ServiceLoader internals that enable runtime discovery and instantiation of providers.
This guide explains Java's Service Provider Interface (SPI), detailing its purpose for decoupling implementations, step-by-step project setup, code examples, configuration files, and an in-depth analysis of ServiceLoader's internal mechanisms, enabling developers to create flexible, extensible Java applications.
This article walks through the background of Spring Cloud's Feign client, explains its core concepts, shows step‑by‑step project setup with Eureka services, demonstrates remote calls and file upload extensions using Feign‑Form, and concludes with a functional microservice example.
This article examines how the misuse of Java Stream and Lambda APIs can make code harder to read and maintain, and provides practical techniques such as proper line breaks, function extraction, careful filter logic, correct Optional usage, and cautious parallel stream adoption to keep code both elegant and efficient.
This article examines the challenges of locating and diagnosing SQL statements in large systems and introduces a lightweight, non‑intrusive MyBatis plugin that injects color‑marking metadata into SELECT, INSERT, UPDATE and DELETE queries, enabling rapid business source identification and enhanced debugging.
This article explores why many developers rarely use thread pools, demonstrates a SpringBoot‑Dubbo demo to reveal hidden thread pools in web containers and RPC frameworks, and offers practical guidance on when to tune existing pools versus adding custom ones for optimal performance.
By using the JavaCompiler API to compile source files at runtime together with a custom ClassLoader that loads the generated bytecode, developers can hot‑reload changed classes instantly without restarting the JVM, enabling rapid iteration, plugin‑style extensions, and faster development cycles.
This article explains the structure, contents, and characteristics of Java's Class constant pool and runtime constant pool, detailing how literals and symbolic references are stored, how the runtime pool can be dynamically modified, and the impact on memory and JVM linking.
This article explores ten effective techniques for handling null values in Java, ranging from traditional if‑else checks to modern Optional usage, Lombok annotations, AOP interceptors, the Null Object pattern, Guava utilities, Kotlin‑style safety, and JDK 14 preview features, helping developers write cleaner, more robust code.
This article explains why large SQL IN clauses cause performance issues or errors in MySQL and Oracle, and demonstrates a Spring Boot 3 solution that uses custom annotations, an AOP aspect, multithreading, and result handlers to automatically split and process the queries in batches.
This article introduces Java 21's virtual threads, explains their lightweight and high‑concurrency advantages, demonstrates basic and delayed usage with code examples, shows how to enable them in Spring Boot, compares performance against traditional threads, and offers additional Java performance‑tuning techniques.
Java 21’s virtual threads provide lightweight, high‑concurrency execution managed by the JVM, enabling developers to create hundreds of thousands of threads with minimal overhead; this article explains their basics, demonstrates Spring Boot integration, compares performance against traditional threads, and shares additional Java optimization techniques.
This article explains why workflow orchestration is essential for isolating business logic in large systems, outlines common pitfalls of tangled if‑else code, and demonstrates how to configure and execute flow chains using a Java flow engine and plugin extensions.
This guide walks Java developers through preparing the environment, installing the CodeGPT plugin, configuring DeepSeek API keys and models, and using the AI assistant for code generation, completion, explanation, and troubleshooting directly within IntelliJ IDEA, while also showing usage statistics.
This article examines three leading Java AI frameworks—LangChain4j, Spring AI, and Agent-Flex—by comparing their architectures, core capabilities, and ideal use‑cases, helping developers choose the most suitable solution for enterprise, domestic, or rapid‑prototype projects.
This article introduces a Java library that simplifies file download functionality in Spring MVC and WebFlux by using a single @Download annotation, handling various source types, concurrent loading, compression, and response writing through a flexible, reactive handler chain architecture.
This article explains the evolution of Java virtual threads in AJDK, details performance improvements, examines pinning problems caused by synchronization and native code, provides migration steps, configuration tips, and code examples, and introduces diagnostic tools for troubleshooting virtual thread issues.
The CMS (Concurrent Mark Sweep) garbage collector, designed for low‑latency old‑generation reclamation, suffers from memory fragmentation, floating garbage, high CPU usage, concurrent‑mode failures, Full GC risks, and complex tuning, making it unsuitable for many production Java workloads.
This article demonstrates how to use Byteman’s DO execution module on the Chaos Mesh platform to invoke static or instance methods of external Java classes without modifying the original code, covering reflection, ClassLoader tricks, and a complete BTM rule example.
This article introduces a comprehensive Spring Boot 3 practical case collection and walks through building a reentrant, auto‑renewing distributed lock using Redis and Lua scripts, providing full code snippets and configuration guidance for robust backend concurrency control.
This article introduces Apache Tika's capabilities for parsing a wide range of file formats, automatic type detection, OCR and language detection, then demonstrates how to integrate Tika into a Spring Boot service to extract text and identify sensitive information such as ID numbers, credit cards, and phone numbers.
Java 8 enriches the Map interface with default methods such as getOrDefault, forEach, merge, putIfAbsent, compute, computeIfAbsent, computeIfPresent and replace, allowing developers to retrieve values with fallbacks, iterate entries, combine or conditionally update entries, and thus write more concise, readable code with far less boilerplate.
A ConcurrentHashMap is internally thread‑safe, so a volatile declaration is only required when its reference may be reassigned (or the field is final), while Spring singleton beans with mutable fields are not thread‑safe and should be made stateless, prototype‑scoped, or synchronized for composite operations.
This article explains Java 21 virtual threads, demonstrates how to create and use them in plain Java and Spring Boot, compares their performance against traditional threads in large‑scale and HTTP workloads, and offers additional Java performance optimization tips.
This article introduces a continuously updated Spring Boot 3 case collection and provides a step‑by‑step guide to nine Java string‑formatting methods—including String.format, MessageFormat, text blocks, number grouping, rounding, zero‑padding, printf, whitespace, and concatenation—complete with runnable code examples.
This article explains the concepts, advantages, design choices, database strategies, and step‑by‑step implementation of a multi‑tenant system using Java Spring Boot and Spring Cloud, including code samples for data sources, dynamic routing, and tenant management in cloud environments.
This step‑by‑step guide shows Java developers how to prepare their environment, install the CodeGPT plugin, configure DeepSeek with an API key and model settings, and then use the assistant for code generation, completion, explanation, question answering, and usage monitoring within IntelliJ IDEA.
An in‑depth comparison of Java’s Hashtable and HashMap covers their thread‑safety mechanisms, null‑key/value policies, inheritance hierarchy, default capacities, resizing strategies, and iterator behavior, highlighting performance trade‑offs and best‑practice alternatives for concurrent applications.
This article explains how enabling Java method breakpoints in IntelliJ IDEA can increase startup time from under two seconds to over thirty seconds, why the JVM design causes the slowdown, and provides practical steps—removing method breakpoints, disabling method‑exit events, and using line breakpoints—to restore fast debugging performance.
This article discusses Meituan's spring recruitment numbers, then provides detailed Java backend interview questions and answers covering Spring MVC vs Spring Boot, MySQL MVCC, Redis Zset implementation, message queue reliability, HashMap internals, and thread pool usage, offering practical insights for candidates.
This article introduces the Liteflow rule engine, explains its architecture and configuration, demonstrates how to define components and EL rule files, and shows a real e‑commerce workflow example, while also providing Maven dependency snippets and usage guidelines for Java Spring Boot applications.
This article demonstrates how to use the iTextPdf library in a Java SpringBoot project to create PDF templates, dynamically fill fixed and tabular invoice data, generate separate PDFs, and merge them into a single document, providing complete code examples and configuration details.
Because phone numbers are identifiers that can contain symbols and exceed the numeric range of an int, storing them as a String—despite higher memory use—is semantically correct, avoids overflow, preserves formatting, and benefits from JVM string pooling, making String the preferred type in most Java applications.
This article explains the LeetCode Combination Sum II problem, detailing how to find all unique candidate combinations that sum to a target using sorting and backtracking while eliminating duplicate results, and provides complete implementations in Java, C++, C, and Python.
This article explains the CQRS pattern, its origins, benefits, and challenges, and provides a step‑by‑step guide with Java code examples on how to implement CQRS, event sourcing, and asynchronous communication using Spring Boot, Axon, and Kafka in microservice architectures.
This article provides a comprehensive guide to Java thread pools, explaining their purpose, construction parameters, execution flow, worker reuse, task retrieval with timeout, lifecycle states, shutdown mechanisms, monitoring methods, and best practices for customizing pools in real-world projects.
This guide explains common scenarios for using custom Java annotations—such as logging, permission control, data validation, and caching—and walks through the step-by-step process of defining an annotation, applying it in Spring services, handling it with an AOP aspect, and testing the implementation in a Spring Boot application.
This guide shows how to use JSONPath within a Spring Boot 3.4.0 project to efficiently query, filter, and modify complex JSON structures, providing Maven setup, syntax overview, operator tables, and practical code examples for extracting authors, prices, books, and applying custom filters.
The Concept‑Download library lets SpringBoot developers replace verbose download code with a single @Download annotation that automatically handles classpath resources, local files, HTTP URLs, custom objects, compression and reactive streaming, simplifying batch and QR‑code ZIP exports.
This article introduces several advanced IntelliJ IDEA debugging techniques—including Evaluate and Log at breakpoints, field breakpoints, exception breakpoints, and method breakpoints—providing step‑by‑step instructions, code examples, and screenshots to help Java developers debug more efficiently without cluttering source code.
This article showcases a collection of over 100 practical Spring Boot 3 examples, focusing on modern Java Stream techniques such as Stream.ofNullable for null safety, Stream.iterate for infinite sequences, advanced collectors like collectingAndThen, takeWhile/dropWhile, teeing, and summarizingLong, each illustrated with concise code snippets.
Fast‑Retry is a high‑performance Java library that enables asynchronous, multi‑task retry with customizable policies, offering dramatically better throughput than traditional synchronous retry frameworks like Spring‑Retry and Guava‑Retry for large‑scale user‑identity polling scenarios.
This article provides a comprehensive guide to Java I/O streams, covering the distinction between node (low‑level) and processing (high‑level) streams, byte versus character streams, their superclasses, common implementations, buffering techniques, object serialization, and practical code examples for reading and writing data.
The article explains the concept of Rump‑Up in performance testing, details the steps to modify multithreaded task and executor classes, and provides Java code examples that enable gradual load increase and controlled data collection for more accurate bottleneck identification.
This article explains Redis Pipeline—a technique that batches multiple commands in a single request to cut round‑trip latency, details how to implement it in Java using Jedis, and outlines its advantages, drawbacks, and ideal scenarios for high‑throughput backend applications.
The article explains how excessive if‑else logic in multi‑business middle‑platforms leads to maintenance nightmares and demonstrates, with concrete code and a real open‑source project, how a flow engine and plugin‑extension framework provide clean isolation, extensibility, and reliable execution of business processes.
This article provides a detailed tutorial on using Maven for Java projects, covering basic configuration, repository setup, dependency management, module organization, plugin usage such as jar, assembly, and shade, as well as build settings and code examples.
This article examines how Java Stream and Lambda, while powerful for concise data processing, can become cumbersome when misused, and provides practical tips such as proper line breaks, function extraction, careful filter logic, safe Optional handling, and cautious use of parallel streams to keep code readable and maintainable.
This article introduces MybatisX, an IntelliJ IDEA plugin that streamlines MyBatis and MyBatis‑Plus development, and provides a detailed step‑by‑step tutorial on setting up a Spring Boot project, configuring the database, generating code, and writing a simple controller using MyBatis‑Plus.
The article explains why excessive conditional logic harms maintainability, introduces a flow‑engine and plugin‑extension architecture to isolate business code, demonstrates configuration and execution with Java examples from the open‑source MemberClub project, and lists the surrounding tech stack for practical learning.
This article explains the concept of Single Sign-On, its advantages, and two practical implementations using ticket‑based authentication and encrypted user data exchange between Service A and Service B, complete with database schema, configuration files, and full Java code examples.
Even when you replace HashMap with ConcurrentHashMap and use ThreadLocal for per‑thread data, hidden pitfalls in thread‑pooled environments can cause data leakage and race conditions, but proper cleanup and atomic operations can restore safety, as demonstrated with concrete Java examples.
This article walks through the problem of locking out users after multiple failed login attempts, explains why IP‑based locking with Redis and Lua scripts is effective, and provides a complete Spring Boot implementation—including front‑end HTML, custom annotations, AOP aspect, Redis configuration, and sample controller code—to enforce a configurable login‑attempt limit.
This article explains the purpose, usage patterns, and internal mechanics of Spring's @Import annotation, including importing regular classes, ImportSelector implementations, and ImportBeanDefinitionRegistrar implementations, with complete code examples and a discussion of how Spring processes these imports at runtime.
The article demonstrates how to refactor a large PHP API suite into a Java Spring MVC application by creating a generic AggregateController that, through model‑name mapping, reflection‑based repository registration and a thread‑safe MappingKit, provides CRUD endpoints for any table, collapsing hundreds of endpoints into just two controllers for client and admin.
This guide walks Java developers through preparing the environment, installing the CodeGPT plugin, configuring DeepSeek API keys and models, and using the AI assistant for code generation, completion, explanation, and troubleshooting within IntelliJ IDEA, complete with screenshots and sample code.
DeepSeek4j 1.4 introduces a Java‑native framework that fully preserves DeepSeek's chain‑of‑thought and billing features, adds reactive streaming support, and provides a Spring Boot starter for effortless integration, accompanied by quick‑start code, configuration examples, and a built‑in debugging UI.
This article explains why Lombok's @Builder annotation ignores field default values in Java classes, demonstrates the issue with sample code, and shows how using @Builder.Default resolves the problem by generating static default methods in the compiled builder class.
This article explains how Java handles string literals and the new String() constructor, detailing when objects are created in the string constant pool versus the heap, and demonstrates the resulting reference comparisons with code examples.
This article explains the design and Java Spring‑Boot implementation of a business transaction ID generator that combines business type, date, random digits and a non‑sequential long integer, discusses database schema, concurrency handling, performance testing, and potential duplication pitfalls.
This article records and analyzes how upgrading an application to JDK 11 changed the Direct Memory management strategy, causing a sharp increase in memory‑utilization alerts, and demonstrates step‑by‑step troubleshooting, code inspection, and JVM parameter tuning to restore normal memory usage.
This article provides a comprehensive guide to IntelliJ IDEA, covering basic operations, advanced shortcuts, Maven integration, debugging, hot‑reload settings, and various UI customizations, offering developers practical tips and code snippets to boost Java development efficiency.
This article explains how SpringBoot's default Tomcat container can be swapped for the high‑performance Undertow server, details Undertow's characteristics, provides Maven configuration steps with code snippets, and presents benchmark results showing superior throughput and lower memory usage for high‑concurrency applications.
This tutorial explains what Spring AI is, walks through creating a Spring Boot project with Maven, adding the necessary dependencies, writing a simple controller that forwards user messages to a local DeepSeek model, configuring the application, and testing the AI‑powered endpoint.
This article introduces the URule rule engine, explains its core concepts, shows how to install and configure it in a Spring Boot project, demonstrates library definitions, rule set creation (wizard and script modes), decision table usage, and provides real‑world scenario code examples for backend developers.
The article explains why existing Java AI frameworks struggle with DeepSeek R1’s chain‑of‑thought and streaming features, introduces DeepSeek4j 1.4 as a targeted solution, details its core capabilities, and provides a step‑by‑step guide to integrate it with Spring Boot and Project Reactor.
This article explains the default Tomcat settings in Spring Boot 2.7.10, details core parameters such as connection queue length, max connections, thread pool sizes, keep-alive and timeout options, and demonstrates how to inspect and test these configurations with code examples and command-line tools.
This article walks through creating a fully automated Spring Boot and MyBatis code generator using Freemarker templates, detailing each step from extracting table metadata to generating DAO, service, controller, and entity classes, and shows how a single-table CRUD can be produced in seconds.
This tutorial explains how to implement dynamic master‑slave MySQL switching in a SpringBoot 3.0.4 project using AOP and a custom @DataSource annotation, covering configuration, enum definitions, utility classes, aspect handling, and usage examples for both single and multiple data sources, including Oracle integration.
This article introduces a Spring Boot 3 case collection with over 100 permanent examples and then provides a complete tutorial on implementing audit logging using Spring AOP, SpEL, asynchronous processing, custom annotations, JPA entities, and batch persistence to efficiently record operation details.
This tutorial walks you through creating a Java‑based AI chat agent using Spring AI Alibaba, integrating Alibaba Cloud's large language model, adding function‑calling for weather queries, and enabling full observability with ARMS in a cloud‑native deployment.
This article explains why the "class file has wrong version" error occurs when Java compilation and runtime versions differ, shows the mapping between Java releases and class file versions, demonstrates the error with sample code, and provides step‑by‑step solutions including version checks, Maven configuration, IDE settings, and best‑practice recommendations.
The JD App backend hotkey framework provides millisecond‑level detection of bursty hot data, users, and interfaces, pushes the hot keys to all JVMs in the cluster, and dramatically reduces database query pressure while improving overall application performance.
This article demonstrates how Java 8’s functional interfaces, such as Function and SFunction, can be leveraged to refactor repetitive data validation logic, introducing generic methods like ensureColumnValueValid and validateColumnValueMatchesExpected that improve code reuse, readability, and maintainability in backend services.
The article explains how automatic @Autowired injection can tightly couple domain models to the Spring container, hide dependencies, hinder testing, create circular‑dependency risks, and violate clean architecture, then demonstrates an explicit‑dependency approach with a custom SpringContext utility, compares both methods, and offers practical guidelines for layered design and testing.
