This article compiles a large set of interview questions frequently asked by top tech companies, covering Java fundamentals, multithreading, Spring framework, MyBatis, Redis, and related concepts, and provides a free QR‑code link for downloading the complete question set with answers.
This article examines Redis's transition from a single‑threaded reactor to a multi‑threaded I/O model, details the underlying I/O multiplexing and BIO subsystems, and explains the lazyfree mechanism for asynchronous large‑key deletions, providing extensive code analysis and performance insights.
This article explains how Redis evolved from a single‑threaded event‑loop architecture using I/O multiplexing and the Reactor pattern to a multi‑threaded I/O model and an enhanced BIO system with lazyfree, detailing design decisions, source‑code excerpts, performance impacts, and practical lessons for developers.
This article explains Java multithreading safety issues, demonstrates synchronized methods, blocks, static methods, mutex locks, deadlock scenarios, and the differences between wait() and sleep() with clear code examples and analysis of their effects on thread execution.
The article explains how to achieve million‑level concurrency in Java by focusing on three fundamental problems—task division, synchronization, and mutual exclusion—using real‑world analogies, diagrams, and concrete code examples to illustrate proper multithreaded design.
This article explains Redis's single‑threaded architecture, its limitations, and how Redis 6.0+ adds configurable I/O threads to parallelize read/write handling, detailing the server initialization, event loop, task queues, and the interaction between the main thread and worker threads.
This article explains why Redis, originally designed as a single‑threaded in‑memory database, introduced a multithreaded network layer in version 6.0, covering the historical design, the limits of CPU vs I/O utilization, the role of I/O multiplexing, and the benefits and drawbacks of the new model.
This article explains how Java's ReentrantLock works, detailing the role of the AbstractQueuedSynchronizer framework, the lock's internal architecture, the FIFO wait‑queue implementation, lock acquisition and release processes, and how these mechanisms avoid the herd effect in multithreaded environments.
This article explains thread safety in Java by detailing how the synchronized keyword and various Lock implementations work, covering their underlying JVM mechanisms, lock upgrade paths, optimizations like biased and lightweight locks, and practical differences between synchronized, ReentrantLock, and ReadWriteLock.
This article explains Java multithreading concurrency issues, demonstrates how synchronized methods, synchronized blocks, static synchronization, mutex locks, deadlocks, and the differences between wait() and sleep() work, and provides runnable code examples to illustrate each concept.
This article explains the hardware memory hierarchy, CPU multi‑level caches, cache coherence protocols, and how Java’s memory model abstracts these concepts to ensure thread safety, covering local and main memory, synchronization primitives, and the three core properties of atomicity, visibility, and ordering.
This article presents a comprehensive guide to Python web scraping, covering basic GET and POST requests with urllib2, using proxy IPs, managing cookies, disguising as a browser via custom headers, handling gzip-compressed responses, and accelerating crawls with a simple multithreaded worker pool.
This comprehensive guide explores Java concurrency fundamentals, covering thread creation, lifecycle, synchronization mechanisms, lock implementations, thread-local storage, memory model, atomic classes, common concurrency utilities, and detailed explanations of thread pools, their configurations, states, and best practices, accompanied by over sixty interview-style questions and code examples.
This article explains how to efficiently handle massive data batch updates in Java by splitting large collections into smaller chunks, processing them concurrently with a configurable ThreadPoolExecutor, and controlling execution order, while providing reusable utility code and practical implementation examples.
The article explains why Redis has traditionally been single‑threaded, details the new IO‑thread multithreading model introduced in Redis 6.0, walks through its four processing stages, lists essential INFO monitoring commands, examines memory overhead of strings versus hashes, compares List and Sorted Set ordering, and identifies five key performance‑blocking points.
Node.js runs JavaScript on a single thread, limiting CPU‑intensive tasks, but the worker‑threads module enables developers to spawn hidden threads, offload heavy computations, and prevent main‑thread blocking, with a practical example showing how to parallelize a CPU‑bound task across multiple workers.
Switching from single‑threaded synchronous calls to multithreaded asynchronous execution can boost performance, but it also introduces nine common problems—including missing return values, data loss, ordering issues, thread‑safety bugs, ThreadLocal anomalies, OOM, high CPU usage, transaction failures, and service crashes—that developers must understand and mitigate.
A backend engineer shares a step‑by‑step case study of diagnosing a 20‑second batch‑score query API, then applying three optimizations—index tuning, multithreaded execution, and request‑size limiting—to bring the response time down to under 500 ms.
From a front‑end developer’s viewpoint, this article examines Rust’s learning curve, pros and cons compared with JavaScript/TypeScript, performance benchmarks, multithreading, testing, and real‑world application scenarios such as tooling, WebAssembly, and desktop clients, while also providing learning resources and reference links.
This article explains Java thread pools, covering their advantages, how to create and configure ThreadPoolExecutor, detailed parameter meanings, various built‑in pool types, usage examples, and best‑practice recommendations to avoid resource exhaustion in Java applications.
The article describes a Java developer's experience with severe IntelliJ IDEA slowdown, outlines several configuration changes, plugin management steps, JDK selection, and a multithreaded code fix that together resolve high CPU usage and improve IDE responsiveness.
This article explains how Thread.Sleep works, compares time‑slice and pre‑emptive scheduling, clarifies why Sleep(1000) doesn't guarantee exact wake‑up timing, and shows how Sleep(0) yields the CPU to improve responsiveness in multithreaded applications.
This article explains the core concepts, configurable parameters, and execution workflow of Java's ThreadPoolExecutor, illustrating each setting with analogies, code examples, and step‑by‑step analysis to help developers design safe and efficient thread pools.
This article walks through a real‑world backend performance case, detailing how a batch‑score query API was trimmed from 20 seconds to under 500 milliseconds by adding composite indexes, introducing multithreaded execution, and limiting request batch size.
This article demonstrates how to use Python, urllib, BeautifulSoup, regular expressions, and multithreading to crawl the DouTuBa website, extract the URLs of emoji images, and download over a hundred thousand pictures automatically.
This article explains the concept of locks in iOS, describing their purpose, the actions of acquiring and releasing, common lock types such as spin locks, mutexes, semaphores, and their implementations using OSSpinLock, pthread_mutex, NSCondition, NSLock, recursive locks, and read‑write locks, along with performance considerations and underlying principles.
This article explains how to efficiently handle large‑scale batch updates in Java by splitting the data set, using a thread pool for concurrent processing, and providing reusable utility code, all illustrated with a clear workflow diagram and step‑by‑step examples.
This article presents twelve practical Python code snippets—including regular‑expression validation, list slicing, swapping without a temporary variable, f‑strings, dictionary inversion, multithreading, most‑common element detection, CSV parsing, and more—to help developers write concise, efficient code without lengthy boilerplate.
This article demonstrates how adding two gevent monkey‑patch lines to a feapder spider reduces CPU usage from 121% to 99% while changing the effective thread count from 36 to 12, and discusses the underlying principle, performance trade‑offs, and future directions for coroutine support.
This article explains Netty’s multithreaded Reactor architecture, introduces the underlying concepts such as Channel, ChannelPipeline, and EventLoop, shows how threads are allocated to ChannelHandlers, and demonstrates how to customize thread pools for customer‑service and agent‑side logic in an IM system.
This article explains the concept of CPU cache false sharing, how it degrades performance on multi‑core systems, and provides practical techniques—including cache‑line alignment macros and padding strategies—to prevent it and improve multithreaded application efficiency.
This article summarizes practical problems encountered with HttpRunner—such as YAML parsing errors, missing attributes, duplicate assertions, custom function parameter issues, and performance bottlenecks—and provides detailed debugging steps, code patches, multithreading enhancements, and report‑optimization techniques for large‑scale API test suites.
The article explains that concurrent programming is deeply tied to real-life scenarios and outlines its three core problems—division of work, synchronization, and mutual exclusion—using company organization, task dependencies, and traffic flow analogies, plus Java code examples to illustrate each concept.
This tutorial explains how to use Java and the WebMagic framework to crawl thousands of images from Sogou image search, parse the JSON responses to extract image URLs, and download the pictures locally using multithreaded processing and custom HTTP utilities.
This article presents a detailed benchmark of java.util.concurrent.ConcurrentHashMap under high thread counts, explains the test methodology using a Groovy‑based FunTester framework, shares raw performance numbers, and uncovers that CPU limits and random number generation are the primary bottlenecks.
This article explains how Python concurrency can boost program performance, covering multithreading, multiprocessing, the Global Interpreter Lock, thread safety, thread pools, and practical code examples for speeding up I/O‑bound and CPU‑bound tasks.
This article demonstrates how to generate, read, and analyze a 10 GB file containing age statistics on a machine with only 4 GB RAM, comparing single‑threaded and multithreaded Java implementations, measuring performance, memory usage, and addressing GC and concurrency challenges.
This article walks through generating a 10GB file of age data, reading it line‑by‑line on a machine with only 4GB RAM, and compares a single‑thread counting approach with a multithreaded producer‑consumer design, showing performance gains, memory usage, and practical tips.
The article presents a complete Java solution for generating, reading, and analyzing a 10 GB file of age values (18‑70) on a 4 GB RAM, 2‑core PC, comparing single‑threaded counting with a producer‑consumer multithreaded design that dramatically improves CPU utilization and reduces total processing time.
To eliminate frame drops caused by animated PopupWindow and Snackbar conflicts, the article shows how moving costly view inflation and show/dismiss operations to a dedicated HandlerThread—while still invoking show() on the UI thread—creates a separate UI thread that respects Android’s thread‑checking rules and keeps animations smooth.
This article demonstrates how to accelerate massive MySQL data updates in a Spring Boot application by replacing naïve loops with manual transaction control, multithreaded processing, CountDownLatch synchronization, and UNION‑based SQL batching, achieving up to a five‑fold speed increase.
This article demonstrates how to efficiently update up to 50,000 MySQL records in a Spring Boot‑MyBatis application by comparing simple loops, manual transaction control, multithreaded execution with CountDownLatch coordination, and union‑based batch updates, while analyzing performance and connection‑pool considerations.
This article demonstrates how to dramatically speed up updating tens of thousands of records in a Spring‑MyBatis application by switching from automatic per‑operation commits to manual transaction control, applying multithreaded processing, tuning the Hikari connection pool, and using SQL UNION‑based batch updates.
This article explores twelve practical multithreading use cases in Java, ranging from simple scheduled tasks and listeners to Excel imports, remote call aggregation, user context handling, MDC logging, high‑concurrency simulation, Kafka message processing, atomic counters, and delayed jobs, providing code examples and best‑practice tips for each scenario.
This article presents a Python solution that parses Tencent video URLs, retrieves encrypted TS video segments through a third‑party VIP service, downloads them concurrently, and merges the segments into a playable MP4 file, detailing the required environment, workflow, and complete source code.
This article provides a comprehensive overview of Java concurrency topics, including various lock types, thread lifecycle states, differences between synchronized and Lock/ReentrantLock, thread safety, thread pool creation and customization, as well as practical multithreading use cases.
This tutorial demonstrates how to fetch, clean, and organize King of Glory item data via a public JSON API using Python requests and pandas, then download item images concurrently, and finally generate comprehensive Markdown, Excel, and other documentation formats for easy reference.
Learn how to use Python to crawl the official King of Glory website, retrieve hero equipment data in JSON, download item images via a thread pool, and automatically generate organized Markdown and Excel documentation, complete with code snippets and troubleshooting tips.
This article explains the fundamentals of Android app startup, categorizes cold, hot, and warm launches, identifies performance bottlenecks using tools like ADB, Systrace, and Traceview, and presents concrete optimization strategies for Application creation and splash-screen rendering that reduce launch time by up to 60 percent.
This article explains how Java's LongAdder works, compares its API and performance to AtomicLong, provides usage examples and a benchmark showing its superior throughput under high thread contention, while noting its higher memory cost and appropriate scenarios for adoption.
This article walks through optimizing a slow MySQL batch import by first inserting a list directly, then using grouped inserts, and finally applying multithreaded batch processing with MyBatis, showing code examples and practical tips to reduce import time from over a minute to under ten seconds.
This article outlines ten typical concurrency pitfalls in Java—including SimpleDateFormat thread‑safety, double‑checked locking flaws, volatile atomicity limits, deadlocks, lock release issues, HashMap race conditions, default thread‑pool misuse, @Async thread explosion, spin‑lock CPU waste, and ThreadLocal memory leaks—providing explanations, code examples, and practical solutions for each.
This article explains why Redis achieves high throughput—up to 100,000 QPS—by leveraging in‑memory storage, simple data structures, a single‑threaded event loop with I/O multiplexing, and the optional multithreaded I/O model introduced in Redis 6.0, including configuration details and safety considerations.
This article explains practical Java debugging tricks such as setting conditional breakpoints, using Drop Frame to revisit previous execution points, handling multithreaded breakpoints, configuring remote debugging, and evaluating or modifying expressions on the fly to streamline development and troubleshooting.
This article examines why Java's synchronized keyword can become ineffective when locking on an Integer object, explores how autoboxing and Integer caching cause lock objects to change, and presents reliable alternatives such as class‑level locks or explicit lock maps for safe multithreaded programming.
This article explains how to build a flexible Java utility for exporting large volumes of report data to Excel using Apache POI, covering customizable headers, field formatting, multithreaded data retrieval, asynchronous processing, and deployment steps.
Photon is a fast, multithreaded Python web crawler that extracts URLs, files, and intelligence such as emails and social media accounts, offering flexible options, Ninja mode, and extensive command‑line parameters for precise and efficient data harvesting across multiple operating systems.
This article explains the structure of modern CPU caches, the principles of cache lines, associativity, and coherence protocols, and demonstrates how these hardware details affect program performance through multiple code examples covering loop stride, matrix traversal, multithreading, and false sharing.
The article explains how to design a C++‑based multithreaded service that uses Pthreads, channels, and TensorRT to parallelize deep‑learning inference tasks, thereby reducing latency and dramatically increasing throughput for AI applications such as facial‑recognition access control systems.
This article examines how Java's synchronized keyword and ReentrantLock behave when multiple threads invoke two synchronized methods of the same class, exploring scenarios with the same instance, different instances, and Runnable run methods, and summarizing the resulting concurrency rules.
This article explains the fundamental differences between threads and processes, the role of Python's Global Interpreter Lock, and provides a comprehensive guide to using the multiprocessing and concurrent.futures modules—including their main classes, synchronization primitives, and practical code examples—for effective concurrent programming in Python.
This article explains why multiple Spring Boot timers can conflict due to single‑threaded execution, demonstrates the problem with example outputs, and shows how to configure a thread pool and use @Async annotations to run timers concurrently, preventing bottlenecks and avalanche effects.
This article explains JavaScript's single‑threaded nature, introduces the event loop and Web Workers, examines the Comlink library for RPC‑style multithreading, provides detailed source‑code analysis, and demonstrates practical use cases such as exporting large Excel files without blocking the UI.
This article explores the inner workings of Linux's glibc malloc, detailing how heap memory is requested from the kernel, how multithreaded support is implemented with per‑thread arenas, and the structures such as arenas, bins, and chunks that together determine allocation efficiency.
The article explains how to create a lightweight custom waiting utility in Java (using Groovy syntax) that repeatedly checks a condition every 0.5 seconds, simplifying thread synchronization for performance testing of multithreaded code.
This tutorial walks you through building a Python scraper that extracts video titles and URLs from Pear Video, then downloads the videos to your computer using single‑threaded requests, a thread‑pool, and asynchronous asyncio techniques, complete with full code examples.
C++11 smart pointers—unique_ptr, shared_ptr, and weak_ptr—replace manual new/delete by providing exclusive, shared, and non‑owning ownership semantics, automatically preventing leaks and dangling references, simplifying multithreaded code, and, when used with best‑practice guidelines, avoid common pitfalls such as double deletions and cyclic dependencies.
This article explains why Spring Boot's default scheduled tasks run on a single thread and demonstrates three practical ways to configure multithreaded scheduling using SchedulingConfigurer, application properties, and the @Async annotation with a custom thread pool.
Photon is a fast, multithreaded Python web crawler that extracts URLs, files, and various intelligence from targets, offering flexible options, Ninja mode, and extensive command‑line parameters while supporting Linux, Windows, macOS, and Termux environments.
This comprehensive guide traces the evolution of computing from early mechanical calculators to today's CPUs, delving into binary systems, memory hierarchies, synchronization primitives, thread states, lock mechanisms, and Java concurrency intricacies, while providing code examples, diagrams, and interview insights for developers.
This article explains CPU cache levels, cache line concepts, coherence protocols, and how cache‑friendly or cache‑unfriendly code patterns—including false sharing and stride access—affect program performance on modern multicore processors.
This article explains how to use SLF4J's MDC feature to attach a request ID to log entries, enabling fast filtering of all logs belonging to a single request even across asynchronous threads and thread pools, and shows a decorator‑based solution for proper propagation.
This article explains why Spring Boot's default single‑threaded scheduler can cause timer conflicts in real‑world applications and demonstrates how adding @Async annotations together with a custom ThreadPoolTaskExecutor configuration enables concurrent execution of multiple scheduled tasks.
This article explains the principles of Java's ReentrantReadWriteLock, details lock downgrade and upgrade mechanisms, provides a full source analysis of read and write lock implementations, and presents a custom upgradable lock with test code and performance observations.
This article explains how to redesign the FunTester framework to enable real‑time pressure scaling by treating each multithreaded task as a manageable object, adding interrupt capabilities, and implementing global management for dynamic thread addition, removal, and cloning during load testing.
This article explains the concepts of spin locks and mutexes, introduces the CLH lock as a fair spin lock used in Java's AbstractQueuedSynchronizer, and provides a detailed step‑by‑step walkthrough of its initialization, lock acquisition, release, testing, and common pitfalls with illustrative code and diagrams.
The article explains Java’s variable‑visibility problem in multithreaded code, describes the Java Memory Model and the happens‑before rules, and shows how synchronization or declaring a field volatile (as in double‑checked‑locking Singleton) guarantees that updates become visible across threads and prevents instruction reordering.
This tutorial shows how to use Python to crawl Douban's Top250 movie list, handle anti‑scraping measures, extract detailed fields, store the data in Excel, and perform data cleaning, statistical analysis, and visualizations such as year distribution, rating trends, and genre word clouds.
This article explains how variable sharing in multithreaded Java programs leads to thread‑unsafe behavior, explores the JVM memory model and stack frame structure, and demonstrates practical ways to achieve thread safety by keeping variables thread‑local or using proxy objects.
This article details the design and implementation of a dynamic pressure model for the FunTester performance testing framework, covering the goal of flexible load adjustments, core features, multithread synchronization using Phaser, code examples, a demo execution, console output analysis, and identified limitations.
This article demonstrates three progressive techniques—direct list insertion, grouped batch insertion, and multithreaded batch insertion—using MyBatis to dramatically reduce MySQL bulk‑import time from over a minute to under ten seconds while handling packet size limits.
This article delves into Python's threading module, explaining thread safety, the role of various lock types—including Lock, RLock, Condition, Event, and Semaphore—along with their methods, usage patterns, common pitfalls like deadlocks, and practical code examples to illustrate proper synchronization techniques.
This article explains the purpose, usage, and real‑world scenarios of Java’s CountDownLatch and CyclicBarrier synchronization aids, illustrating their behavior with relatable analogies and providing guidance on when to apply each construct in multithreaded applications.
This article presents a detailed multi‑threaded performance benchmark of Redis list commands using the FunTester framework, describing three test scenarios, Java implementation details, raw JSON results, and observations on QPS and latency for insert, pop, and combined add‑remove operations.
This article explains how to create a Python web crawler that automatically generates URLs for a drama‑download site, filters out invalid pages, extracts ed2k links using requests and regular expressions, saves them to text files, and employs multithreading to speed up processing, while discussing challenges such as duplicate URLs and filename sanitization.
This article explains how to scrape tens of thousands of images from Sogou by analyzing the request URLs, extracting image URLs from JSON responses, and implementing a multithreaded Java downloader that stores the pictures locally.
This article provides a comprehensive tutorial on Python's threading module, explaining thread safety concepts and demonstrating the use of various lock primitives—including Lock, RLock, Condition, Event, and Semaphore—through detailed code examples and practical exercises.
This article explains how Java locks solve concurrent access problems, compares the built‑in synchronized lock with ReentrantLock, describes their upgrade mechanisms, usage patterns, and scenarios, and offers guidance on choosing the appropriate lock for different environments.
This article describes how to build a Python web crawler that automatically generates numeric URLs, checks their validity, extracts download links for TV dramas from cn163.net, saves them to text files, and discusses practical challenges such as regex parsing, filename restrictions, and multithreading performance.
This article explains Java's memory model and compares the volatile keyword, synchronized blocks/methods, and the Lock interface, detailing their visibility, mutual exclusion, performance, and proper usage patterns to avoid deadlocks and improve multithreaded efficiency.
This guide explains how to analyze Sogou's image search XHR request, extract image URLs from the JSON response, and use Java with multithreaded HTTP requests to download thousands of pictures efficiently, including full source code and execution tips.
The article explains Redis 6.0's new features—especially the multithreaded network I/O model—why earlier versions were single‑threaded, how the IO threads cooperate with the main thread, configuration steps, thread‑count recommendations, and the model's limitations and performance implications.
This article compiles 16 classic Java multithreading interview questions covering high‑concurrency containers, CAS and ABA problems, volatile vs synchronized, the Java Memory Model, ThreadLocal drawbacks, AQS, thread‑pool architecture, queue types, sizing strategies, rejection policies, lifecycle management, and graceful shutdown techniques.
This tutorial walks you through creating a feature‑rich desktop music player in Python using PyQt5, covering UI layout design, keyword‑based music crawling, multithreaded downloading, playback controls, volume adjustment, and additional functions like random and repeat modes, all illustrated with complete code snippets and screenshots.
This article explains four Java concurrency utilities—CountDownLatch, CyclicBarrier, Semaphore, and Exchanger—detailing their concepts, typical use cases, and providing complete code examples that demonstrate synchronization patterns such as thread coordination, resource limiting, and data exchange.
The article explains why multithreading is essential for modern CPUs, introduces thread pools to reduce overhead, and details Java's ThreadPoolExecutor creation parameters, execution process, and core methods such as addWorker, runWorker, and getTask, using JDK 1.8 source code examples.
This tutorial walks through designing and implementing a Python desktop music player using PyQt5, covering UI layout, keyword‑based music crawling, multithreaded downloading, playback controls, volume adjustment, and various playback modes such as sequential, random, and repeat.
This article explains the fundamentals of iOS crashes, categorizes common crash types such as wild pointers, deadlocks and watchdogs, presents real-world JD Finance app crash cases with code analysis, and outlines systematic debugging, logging, and preventive practices to keep crash rates well below industry averages.
This article systematically explores concurrency optimization for high‑performance C++ engineering, covering CPU trends, SIMD and out‑of‑order execution, single‑thread parallelism, lock‑free and wait‑free synchronization, and practical case studies of counters and queues to improve multithreaded scalability.
Chaplin Project replaces costly image‑to‑video synthesis on Xianyu by using centrally managed, OpenGL‑shader templates that combine product images with dynamic effects at playback, supported by a visual editor, resource platform, recommendation engine, and multi‑threaded client architecture, delivering richer browsing while conserving resources.
