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Thread Dumps Analysis for Java Applications

Acquisition of thread dumps can be collected multiple times through jstack, kill-3, JConsole or SpringBootActuator and other methods; 2. In the thread state, RUNNABLE may correspond to high CPU or infinite loops, BLOCKED indicates lock competition, WAITING/TIMED_WAITING is a waiting state, so you need to pay attention to exception accumulation; 3. Deadlock will be clearly indicated by jstack, which is manifested as a loop waiting lock, which should be solved by unified lock sequence or reduced lock granularity; 4. High CPU threads need to combine top and hexadecimal conversion positioning to check whether there are regular backtracking, serialization and other time-consuming operations in the call stack; 5. A large number of BLOCKED threads point to the same lock object to indicate lock competition

Aug 01, 2025 am 04:24 AM

The Ultimate Guide to Java Exception Handling

Javaexceptionhandlingensuresrobustandmaintainableapplicationsbyproperlymanagingruntimeerrors.1.TheThrowableclassistheparentofallexceptions,withErrorforJVM-levelissueslikeOutOfMemoryErrorandExceptionforrecoverableconditions.2.Checkedexceptions(e.g.,IO

Aug 01, 2025 am 03:50 AM

java Exception handling

Java Message Service (JMS) with ActiveMQ Tutorial

JMSwithActiveMQenablesasynchronous,looselycoupledcommunicationinenterpriseapplicationsbyusingmessaging;thistutorialdemonstratessettingupActiveMQandimplementingapoint-to-pointmessagingexampleusingtheJMSAPI.1.JMSisaJavaAPIsupportingtwomodels:Point-to-P

Aug 01, 2025 am 03:42 AM

Securing REST APIs with Spring Security and Java

Disable sessions and CSRF, use SessionCreationPolicy.STATELESS and csrf().disable() to achieve REST-friendly and secure; 2. Use JWT for stateless authentication, generate and verify tokens containing user roles and expiration time through JwtUtil; 3. Create a JwtAuthenticationFilter to intercept requests, parse the Bearer token in the Authorization header, and store the authentication information into the SecurityContextHolder after verification; 4. Use @PreAuthorize("hasRole('ADMIN')"

Aug 01, 2025 am 03:31 AM

what is the synchronized keyword in java

The synchronized keyword in Java is used to control access to shared resources in a multi-threaded environment. Its core function is to ensure that only one thread can execute a certain method or code block at the same time, thereby preventing data competition and ensuring data integrity. 1. Synchronized realizes this function through the locking mechanism: when a thread enters the synchronized method or code block, it will acquire the lock of the object, and other threads must wait for the lock to be released before entering; 2. It can be used for instance methods, static methods and code blocks, corresponding to different lock objects (instances, classes, and custom objects); 3. When using it, you need to pay attention to avoid deadlocks, reduce performance overhead, and reasonably control the granularity of the lock; 4. In actual applications, it is often used.

Aug 01, 2025 am 03:22 AM

The Ultimate Guide to Java Interview Questions for Senior Developers

Masterconcurrencybyunderstandingsynchronized,ReentrantLock,andStampedLocktrade-offs,useJMMknowledgetoensurethreadsafety,andapplytoolslikejstackfordeadlockdetection.2.DemonstrateJVMexpertisebyexplainingmemorystructure,choosingappropriateGCslikeZGCforl

Aug 01, 2025 am 02:58 AM

java interview

A Deep Dive into the Java Memory Model

TheJavaMemoryModel(JMM)defineshowthreadsinteractwithmemory,governingvisibility,ordering,andatomicityofvariableupdatesacrossthreads.2.Withoutpropersynchronization,onethreadmaynotseeanother’schangesduetocachingorinstructionreordering.3.Thehappens-befor

Aug 01, 2025 am 02:51 AM

Effective Java Exception Handling Best Practices

The detected exception is used to recoverable scenarios to avoid abuse to prevent increased complexity; 2. Throw specific exception types instead of generalized exceptions to improve readability and maintenance; 3. The exception message should be specific, contains parameter values and does not expose sensitive information; 4. Errors should be thrown as soon as possible, and the capture should be delayed to a position that can be processed; 5. It is prohibited to ignore exceptions, logs should be recorded or try-with-resources should be used; 6. All AutoCloseable resources must be managed with try-with-resources; 7. Convert exceptions at abstract boundaries and retain root causes; 8. Exceptions or return should not be thrown in finally blocks to avoid covering up exceptions; 9. Custom exceptions should be immutable and provide a complete constructor and gett

Aug 01, 2025 am 02:28 AM

java Exception handling

Handling JSON in Java Efficiently with Jackson and Gson

Jacksonisfasterandmoreconfigurable,makingitidealforhigh-performance,framework-integratedapplicationslikeSpring;2.Gsonofferssimplicityandeaseofuse,bettersuitedforsmalltomediumappsorAndroiddevelopment;3.ReuseObjectMapperorGsoninstancesforefficiency;4.U

Aug 01, 2025 am 02:11 AM

java json

Advanced Java Generics: Taming Wildcards and Type Erasure

Wildcards and type erasure in Java generics can be effectively mastered through PECS principles and type tokens. Use ?extendsT to read data and ?superT to write data, and follow the Producer-ExtendsConsumer-Super principle; 1. Unbounded wildcards are used in scenarios where only Object methods are operated, and elements cannot be added; 2. Upper bounded wildcards

Aug 01, 2025 am 02:05 AM

java generics Type erasure

How to Monitor a Java Application with Prometheus and Grafana

TomonitoraJavaapplicationwithPrometheusandGrafana,firstinstrumenttheappusingMicrometerbyaddingmicrometer-registry-prometheusandSpringBootActuatordependencies,thenexposethe/actuator/prometheusendpointviaconfigurationinapplication.yml.2.SetupPrometheus

Jul 31, 2025 am 09:42 AM

java monitor

What's New in Java 21: A Comprehensive Guide

VirtualThreads (official version) significantly simplifies high-throughput concurrent programming, suitable for I/O-intensive tasks; 2. StructuredConcurrency (official version) improves the readability and security of concurrent code to avoid zombie threads; 3. StringTemplates (preview version) replaces String.format, making it safer to verify when compiling; 4. SequencedCollections API (official version) unified and ordered collection operations such as getFirst and reversed; 5. Other new additions include ScopedValues, RecordPatterns and GeneralZGC. It is recommended to be as soon as possible

Jul 31, 2025 am 09:32 AM

The Future of Java: Trends and Predictions

The future development trends of Java include: 1. The release model centered on the LTS version, and enterprises will mainly adopt long-term support versions such as Java17 and Java21; 2. ProjectLoom introduces virtual threads to greatly improve concurrency performance and simplify the programming model; 3. Enhance cloud-native and microservice support through GraalVM, Quarkus and other technologies to reduce resource consumption; 4. Continue to introduce modern language features such as record classes, pattern matching, sealing classes, etc. to improve expression and security; 5. Although JVM languages such as Kotlin and Scala have risen in specific fields, Java still maintains the dominant position of enterprise development with its ecological advantages; overall, Java is maintaining its enterprise-level and post-end through continuous evolution.

Jul 31, 2025 am 09:21 AM

Securing Java REST APIs with Spring Security and JWT

Implementing the JWT-based RESTAPI security mechanism in SpringBoot applications, first of all, you need to understand that the server issues the JWT after the user logs in, the client carries the token in the Authorization header of subsequent requests, and the server verifies the validity of the token through a custom filter; 2. Add spring-boot-starter-security, spring-boot-starter-web and jjwt-api, jjwt-impl, and jjwt-jackson dependencies in pom.xml; 3. Create a JwtUtil tool class to generate, parse and verify JWT, including extracting usernames, expiration time, generating tokens and proofing

Jul 31, 2025 am 09:13 AM