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Java Concurrency in Practice: The Executor Framework

ExecutorFramework is a concurrency tool in Java for simplifying thread management and task scheduling. Its core is to decouple task submission from execution. 1. The reasons for using Executor instead of newThread() include avoiding resource out of control, improving performance, realizing thread reuse and unified management; 2. The main interfaces are Executor and the extension interface ExecutorService, which supports task submission, life cycle management and return of Future results; 3. Common thread pool types include newFixedThreadPool, newCachedThreadPool, newSingleThreadExecutor and newSc

Jul 31, 2025 am 01:52 AM

java concurrent

GraphQL APIs with Java and Spring for GraphQL

First, choose SpringforGraphQL for its official support, annotation driver, zero configuration startup, compatibility and ease of testing; 1. Add spring-boot-starter-graphql dependency and optionally add Web and GraphiQL support; 2. Define Query and Book types in schema.graphqls; 3. Create Book classes and use Lombok to simplify the code; 4. Use @Controller and @QueryMapping to implement bookById and allBooks queries; 5. After starting the application, use http://localhost:8080/graphi

Jul 31, 2025 am 01:46 AM

Java Memory Management and Avoiding Memory Leaks

Java memory leaks mainly occur in the heap area. Common scenarios include static collection classes holding object references, not closing resources, not logged out of the listener, implicitly holding external class references, and improper use of ThreadLocal; 2. The solutions are: using weak references or limiting cache size, using try-with-resources to automatically close resources, manually logging out listeners or using weak references, declaring the internal class as static, and using remove() to clean ThreadLocal; 3. Detection methods include using jstat/jmap/jvisualvm and other JVM tools, EclipseMAT to analyze heap dump files, and enabling GC logs to observe memory changes; 4. The best

Jul 31, 2025 am 01:22 AM

memory leak java memory management

Java Message Service (JMS) with ActiveMQ for Asynchronous Communication

JMS is the message communication API standard of the Java platform, supporting point-to-point and publish/subscribe models, and ActiveMQ is the message middleware it implements; 1. Start ActiveMQ service and listen to the default port; 2. Add activemq-client dependency in the Maven project; 3. Create producers to send messages to queues through ConnectionFactory; 4. Create consumers to receive messages asynchronously through MessageListener; this combination realizes system decoupling, traffic peak cutting, reliable delivery and asynchronous processing, and is suitable for traditional Java enterprise applications. Although there are more modern alternatives, they still have learning and use value.

Jul 31, 2025 am 01:14 AM

Implementing a Caching Layer in a Java Application with Redis

RedisisusedforcachinginJavaapplicationstoimproveperformancebyreducingdatabaseloadandenablingfastdataretrieval.1.InstallRedisusingDocker:dockerrun-d-p6379:6379redis.2.Addspring-boot-starter-data-redisandlettuce-coredependenciesinpom.xml.3.ConfigureRed

Jul 30, 2025 am 03:30 AM

Building RESTful APIs in Java with Jakarta EE

SetupaMaven/GradleprojectwithJAX-RSdependencieslikeJersey;2.CreateaRESTresourceusingannotationssuchas@Pathand@GET;3.ConfiguretheapplicationviaApplicationsubclassorweb.xml;4.AddJacksonforJSONbindingbyincludingjersey-media-json-jackson;5.DeploytoaJakar

Jul 30, 2025 am 03:05 AM

java

How to Manage Dependencies in a Large-Scale Java Project

UseMavenorGradleconsistentlyforreliabledependencymanagementwithclearscopesandcentralizedconfiguration.2.Structurelargeprojectsintomulti-moduleswithaparentPOMorrootprojecttomanageshareddependenciesandenablereusewhileavoidingcycles.3.Strictlycontrolver

Jul 30, 2025 am 03:04 AM

Comparing Java, Kotlin, and Scala for JVM Development

Kotlinoffersthebestbalanceofconcisesyntaxandreadability,reducingboilerplatecomparedtoverboseJava,whileavoidingScala’scomplexityandreadabilityissues.2.JavaandKotlinleadinecosystemintegrationwithfullsupportforframeworkslikeSpringandAndroid,whereasScala

Jul 30, 2025 am 03:00 AM

How to use Java MessageDigest for hashing (MD5, SHA-256)?

To generate hash values using Java, it can be implemented through the MessageDigest class. 1. Get an instance of the specified algorithm, such as MD5 or SHA-256; 2. Call the .update() method to pass in the data to be encrypted; 3. Call the .digest() method to obtain a hash byte array; 4. Convert the byte array into a hexadecimal string for reading; for inputs such as large files, read in chunks and call .update() multiple times; it is recommended to use SHA-256 instead of MD5 or SHA-1 to ensure security.

Jul 30, 2025 am 02:58 AM

java

Implementing Authentication and Authorization in a Java Web App

UseSpringSecurityforrobust,standard-compliantauthenticationandauthorizationinJavawebapplications.2.Implementauthenticationviaform-basedloginorJWTforstatelessAPIs,ensuringpasswordsarehashedwithBCryptandtokensaresecurelymanaged.3.Applyauthorizationusin

Jul 30, 2025 am 02:58 AM

Authentication java web

Java NIO and Asynchronous I/O Explained

The main differences between JavaNIO and AsynchronousI/O are: 1. JavaNIO adopts Reactor mode, polls ready events of multiple channels through Selector, and uses a single thread to process multiplexed I/O, which is suitable for high-concurrency network servers and fine control; 2. AsynchronousI/O adopts Proactor mode, based on event-driven and callback mechanisms, notifying the completion processor when the operation is completed, truly realizing asynchronous non-blocking, suitable for extremely scalable and low-latency systems; 3. The NIO thread model is simple, has good compatibility, but requires manual management of buffers and states. Although AIO does not need to be polled and has high resource utilization, it is complex in programming, easy to fall into callback hell and relies on operations.

Jul 30, 2025 am 02:50 AM

異步i/o java nio

What is the super keyword in Java?

The super keyword is used in Java to refer to the parent class of the current object. Its main uses include accessing the parent class method, calling the parent class constructor, and resolving field name conflicts. 1. Access the parent class method: When the child class overrides the parent class method, the parent class version can be called through super.method() to extend its behavior rather than completely replace it; 2. Call the parent class constructor: super() or super(args) is used in the child class constructor to initialize the parent class field, and the statement must be located on the first line of the child class constructor; 3. Resolve field name conflicts: If the child class defines the same name field as the parent class, super.fieldName can be used to explicitly access the parent class field.

Jul 30, 2025 am 02:49 AM

Java Concurrency: Locks, Conditions, and Synchronizers

The Lock interface provides more flexible lock control than synchronized, supporting attempt acquisition, interruption, timeout acquisition and fair lock; 2. Condition allows accurate inter-thread communication through multiple condition variables to avoid false wake-up; 3. Common Synchronizers include CountDownLatch for waiting for multiple tasks to complete, CyclicBarrier for multi-thread synchronization to reach barrier points, Semaphore for controlling the number of concurrent threads, and Phaser for phased synchronization of dynamic threads; when using it, the simplicity of synchronized must be given priority, Lock must combine try-finally to prevent deadlocks, Cond

Jul 30, 2025 am 02:48 AM

Performance Implications of Java Boxing and Unboxing

Boxing will frequently create objects, increasing memory overhead and GC pressure; 2. The cache is only valid for small-scale values such as Integer between -128 and 127, and objects will still be created in large quantities after they are exceeded; 3. Null value checks are required when unboxing, which may cause NullPointerException and bring additional performance losses; 4. The use of wrapper classes in the collection will cause frequent boxing and unboxing during traversal and calculation, affecting the locality of the CPU cache; priority should be given to the use of basic type arrays or native collection libraries such as FastUtil to reduce performance overhead and avoid implicit type conversion in hotspot code.

Jul 30, 2025 am 02:44 AM

java performance