
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
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
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
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
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
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
Building Scalable Java Applications on Google Cloud Platform
Choosetherightcomputeservice—useGKEformicroservices,CloudRunforstatelessapps,orAppEngineforsimplicity,andautomatedeploymentswithCloudBuild.2.LeveragemanagedserviceslikeCloudSQL,Firestore,Pub/Sub,andCloudStoragetoreduceoperationaloverheadandensureinde
Jul 31, 2025 am 09:11 AM
Solving Common Concurrency Issues in Java
Raceconditionsoccurwhenmultiplethreadsaccessshareddata,leadingtoinconsistencies;fixwithsynchronized,AtomicInteger,orReentrantLock.2.Deadlockariseswhenthreadswaitindefinitelyforeachother’slocks;preventbyconsistentlockordering,usingtryLockwithtimeout,a
Jul 31, 2025 am 09:09 AM
Troubleshooting Common Java `OutOfMemoryError` Scenarios
java.lang.OutOfMemoryError: Javaheapspace indicates insufficient heap memory, and needs to check the processing of large objects, memory leaks and heap settings, and locate and optimize the code through the heap dump analysis tool; 2. Metaspace errors are common in dynamic class generation or hot deployment due to excessive class metadata, and MaxMetaspaceSize should be restricted and class loading should be optimized; 3. Unabletocreatenewnativethread due to exhausting system thread resources, it is necessary to check the number of threads, use thread pools, and adjust the stack size; 4. GCoverheadlimitexceeded means that GC is frequent but has less recycling, and GC logs should be analyzed and optimized.
Jul 31, 2025 am 09:07 AM
How to set up a professional Java Development Environment
Install the appropriate JDK (recommended Java17LTS version, use trusted distributions such as EclipseTemurin), set JAVA_HOME and PATH environment variables, and pass java-version and javac-version verification; 2. Select a professional IDE (recommended IntelliJIDEACommunity), configure the compiler, code style and necessary plug-ins such as Lombok and SonarLint; 3. Use the build tools Maven or Gradle to manage dependencies and project structures, it is recommended to use GradleWrapper or install Maven and configure MAVEN_HOME; 4. Install Git and configure user information
Jul 31, 2025 am 09:01 AM
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