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Surviving the Java Coding Interview: Data Structures and Algorithms

Master the core data structure and its applicable scenarios, such as the selection of HashMap and TreeMap, and the expansion mechanism of ArrayList; 2. Practice algorithms from the Java perspective, proficient in double pointer, sliding window, DFS/BFS and other modes and can be clearly implemented; 3. Write clean and robust Java code, pay attention to naming, boundary processing and language features (such as generics and final); 4. Prepare the practical question of "why use Java" and understand the impact of StringBuilder, GC, etc. on performance; maintain practice and clear expression to stand out.

Jul 23, 2025 am 03:46 AM

java interview

Implementing Event-Driven Architecture with Java Kafka

The core points of using Java and Kafka to implement event-driven architecture include: 1. Design a clear event model, use Avro SchemaRegistry to manage structure changes, unify naming specifications and include necessary information; 2. Set reliability parameters, asynchronous sending and log callbacks when building producers, and consumers use Group to achieve expansion, control offset submission and idempotence processing; 3. Use KafkaStreams to implement real-time processing logic, such as window aggregation statistics; 4. Design an error retry mechanism, catch exceptions and retry failure messages, use DLQ to handle multiple failure events, and improve system robustness.

Jul 23, 2025 am 03:43 AM

Mastering the Builder Design Pattern in Java

The Builder mode solves the problem of too many construct parameters and mutability by building complex objects in step by step; 2. When implementing, set the class to final and initialize the fields through Builder in a private construct; 3. Create a static internal Builder class, and each setting method returns this to support chain calls; 4. Verify the required fields in build() to ensure object consistency; 5. Applicable to multiple parameters, especially objects with optional parameters, to improve readability and maintenance, and avoid telescoping constructors or destroying immutability setters.

Jul 23, 2025 am 03:42 AM

java

Static Code Analysis for Improving Java Code Quality with SonarQube

SonarQube detects pre-run vulnerabilities such as null pointers and resource leaks, and integrates CI/CD to automatically analyze PR; 2. Prevent security risks such as hard-coded passwords and unsafe random numbers through OWASP rules, and use SecurityHotspots to enhance team security awareness; 3. Detect code odor, duplicate code, irregular naming problems, reduce cognitive burden, and improve maintainability; 4. Track technical debt and test coverage, monitor coverage >80%, repeat rate

Jul 23, 2025 am 03:37 AM

What is the 'static' keyword in Java used for?

In Java, the static keyword is used to create class-level variables and methods, allowing direct access without instantiation of objects. 1. The static variable is shared by all instances, and modifying it in one place will affect all instances; 2. The static method can be called directly without creating objects, and is suitable for tool classes or constant operations; 3. The static block is used for initialization operations during class loading, such as configuration reading; 4. Be cautious when using it to avoid excessive use and difficult to maintain memory problems and code.

Jul 23, 2025 am 03:36 AM

how to compile and run a java program from command line

TocompileandrunaJavaprogramfromthecommandline,firstensuretheJDKisinstalledandconfigured.1.Checkinstallationbyrunningjavac-versionandjava-version.2.Ifnotinstalled,downloadandinstalltheJDKandsetthePATHenvironmentvariable.3.CompiletheJavafileusingjavacH

Jul 23, 2025 am 03:35 AM

Building Reactive Java APIs with Project Reactor

The key to using ProjectReactor to build a responsive API is to master the following key points: 1. Understand Flux and Mono, which handle asynchronous sequences of 0 to N elements and 0 or 1 element respectively, with lazy loading characteristics; 2. Use non-blocking I/O and backpressure mechanisms to improve performance, avoid blocking calls, and use responsive database drivers such as R2DBC; 3. Reasonably organize the code structure, realize concurrent logic merge by splitting functions, process control operators and .zip() to prevent "callback hell"; 4. Strengthen debugging and error handling, use .log() to track stream events, and use .onErrorResume() and other operators to elegantly handle exceptions to ensure the stability and maintainability of the flow.

Jul 23, 2025 am 03:29 AM

Implementing CQRS and Event Sourcing in Java

CQRS and EventSourcing improve system maintainability and scalability by separating read and write operations and recording state changes. CQRS separates commands and queries to achieve independent expansion; EventSourcing records events instead of final state, enhancing audit and rollback capabilities. When designing a domain model, you need to focus on the aggregate root response command and issue events to keep the service layer light, ensure the event immutable and the aggregate itself to verify the legitimacy. Using AxonFramework can simplify implementation, combine SpringBoot to improve development efficiency, and can also manually build core components. The query side asynchronously updates the read model through Projection, accepting short-term inconsistencies in exchange for performance. Actual development needs to pay attention to event version control,

Jul 23, 2025 am 03:27 AM

Optimizing Java Application Startup Time

Java application slow startup can be solved by positioning bottlenecks and optimizing. 1. Analyze the startup time, use tools such as -Xprof, StartupFailureReporter or JFR to find out the reasons for the slowness; 2. Reduce unnecessary dependencies and automatic configuration, exclude unused SpringBoot automatic configuration classes and clean up the dependency tree; 3. Adjust JVM parameters, such as disabling C1 compilation, skipping bytecode verification, and using G1GC to improve cold startup performance; 4. Use Devtools or hot deployment tools to reduce waiting time in the development environment.

Jul 23, 2025 am 03:27 AM

java Start Time

Java Garbage Collection (GC) Deep Dive

JavaGC automatically recycles memory through accessibility analysis and generational assumptions. MinorGC is fast and frequent, and FullGC is the heaviest to avoid; 2. Judging GC problems, time consumption, Old area trends and STW time, and turning on the log is the prerequisite; 3. Adjust the priority to set the target (throughput or delay), then adjust parameters such as the size of the young generation, Survivor ratio, and Metaspace upper limit, disable System.gc() to accurately locate the problem instead of blindly modifying the parameters.

Jul 23, 2025 am 03:19 AM

java gc

Java Data Structures and Algorithms for Performance

The key to optimizing Java program performance lies in the rational selection of data structures and algorithms. 1. Select appropriate collection classes according to the scene, such as frequent access to intermediate elements, use ArrayList, and use LinkedList to operate head or tail, find multi-priority HashMap or HashSet, and avoid thread-safe classes and capacity expansion losses. 2. Avoid repeated calculations, use memory cache results to reduce time complexity. 3. Master efficient sorting search algorithms, such as insertion sorting, counting sorting, binary search, KMP, etc., and select according to data characteristics. 4. Reduce GC pressure, avoid creating objects in loops, use object pools, StringBuilder and use StreamAPI with caution.

Jul 23, 2025 am 03:09 AM

java algorithm

Enterprise Integration Patterns with Apache Camel and Java

ApacheCamel is one of the best tools for implementing enterprise integration modes (EIPs) in Java. It simplifies common problems such as message routing, conversion, error handling, etc. through smooth DSL; 2. Core advantages include lightweight embedding, 300 connectors, declarative routing (such as Content-BasedRouter), and built-in EIP implementation (such as Splitter/Aggregator, IdempotentConsumer); 3. It is recommended to use it in combination with SpringBoot, which is easy to test, monitor and operate and maintain, making microservice integration more efficient and reliable.

Jul 23, 2025 am 03:09 AM

java

Java Bytecode Instrumentation for Monitoring

Java bytecode instrumentation realizes dynamic analysis of the running status of Java programs by modifying the .class file insertion monitoring logic when class loading. Its core principle is to use the Instrumentation API and bytecode operation libraries (such as ASM, ByteBuddy, etc.) to insert monitoring code before and after the method is executed without modifying the source code. The specific steps include: 1. Use JavaAgent to intercept the class loading process and register the ClassFileTransformer; 2. Insert monitoring logic such as timing, logs, etc. into the target method to ensure that the original logic is not affected; 3. Avoid destroying the method signature or introducing exceptions, and ensure that the bytecode passes JVM verification. Common application scenarios are:

Jul 23, 2025 am 03:02 AM

What is polymorphism in Java with example?

PolymorphisminJava allows objects of different classes to be regarded as objects of common superclasses and is one of the four pillars of object-oriented programming. It reflects runtime polymorphism through method rewriting (such as the different implementations of the sound method of Animal class in Dog and Cat classes), and also reflects compile-time polymorphism through method reloading, making the code more flexible and maintainable, and is widely used in frameworks, GUI event processing, collection operations and design patterns.

Jul 23, 2025 am 02:58 AM

java Polymorphism