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How to remove duplicates from a list in Java?

Use LinkedHashSet to maintain the insertion order and deduplication; 2. Use Java8Stream's distinct() method to be concise and retain the order; 3. Use removeIf combined with HashSet to remove duplicate elements on the original list; 4. For custom objects, you need to rewrite equals and hashCode methods to correctly deduplicate; appropriate methods should be selected according to Java version and coding style, and duplicates in the list can be effectively removed.

Aug 08, 2025 am 12:16 AM

How to create and use annotations in Java

Java annotations are powerful tools for adding metadata to code and can be used for documentation, compilation checking, code generation, or runtime processing. 1. The annotation is defined through @interface, which can contain elements and set default values; 2. Use @Target, @Retention and other meta annotations to control the application scope and life cycle; 3. Read RUNTIME level annotations at runtime through reflection; 4. Use @Repeatable to implement repeated annotations, and container annotations need to be defined; 5. The actual uses include verification, dependency injection, routing, testing and code generation, and retention strategies should be selected as needed to optimize performance.

Aug 07, 2025 pm 10:11 PM

java annotation

How to create a directory in Java?

UseFiles.createDirectories()forcreatingdirectories,asithandlesnestedpathsandispartofthemodernNIO.2API;2.Thismethodcreatesallnecessaryparentdirectoriesanddoesnotthrowanerrorifthedirectoryalreadyexists;3.AlwayshandleIOExceptionwhenusingNIO.2methods;4.O

Aug 07, 2025 pm 08:52 PM

A Guide to Using GraalVM for Polyglot Java Applications

GraalVM is a high-performance multilingual runtime that allows efficient running of Java, JavaScript, Python, Ruby and other languages in a single process and achieve seamless interoperability. 1. Install GraalVM and configure JAVA\_HOME; 2. Use gu command to install the required language runtimes such as Python, JS, and Ruby; 3. Call other language codes in Java through PolyglotAPI and share data; 4. Use native-image tools to compile supported languages (such as JS) into native executable files to improve startup speed and performance; 5. Suitable for script plug-ins, data processing pipelines and other scenarios, but pay attention to memory usage, thread safety and Py

Aug 07, 2025 pm 08:04 PM

Can you explain the diamond problem and how Java 8 addresses it?

Thediamondproblemoccurswhenaclassinheritsconflictingmethodimplementationsfrommultipleinterfacesinadiamond-shapedhierarchy;1)Java8addressesitbyrequiringtheclasstoexplicitlyoverridetheconflictingmethod;2)iftwointerfacesprovidedefaultmethods,themostspec

Aug 07, 2025 pm 07:44 PM

Working with Files and I/O in Modern Java

Modern Java file I/O should use NIO.2 first. 1. Use Path and Paths instead of File; 2. Use Files.readString/writeString (Java11); 3. Use Files.lines() to stream large files with try-with-resources; 4. Use Files.copy/move/delete to operate files; 5. Use Files.newDirectoryStream or Files.walk to traverse the directory; 6. Always handle IOException properly; 7. Follow best practices to avoid manually managing flows, and most operations can use Fil

Aug 07, 2025 pm 07:43 PM

How to throw an exception in Java

TothrowanexceptioninJava,usethethrowkeywordfollowedbyanexceptionobject.1.UsethrownewExceptionType("message")tomanuallysignalanerror.2.Chooseappropriatebuilt-inexceptionslikeIllegalArgumentException,NullPointerException,orIOExceptionbasedont

Aug 07, 2025 pm 07:31 PM

Java and Docker: A Practical Guide

Create a basic Dockerfile, use slim images and correctly configure ENTRYPOINT; 2. Optimize the image size and construction speed through multi-stage construction and layer cache; 3. Reasonably set JVM parameters to adapt to container resource limitations; 4. Use fixed version basic images, non-root user operation, health checks and standard output logs in the production environment; 5. Combined with DockerCompose management dependency services to ensure that applications run efficiently in a consistent, safe and maintainable environment.

Aug 07, 2025 pm 07:26 PM

java docker

Could you clarify the roles of final, finally, and finalize in Java?

finalisakeywordthatrestrictsmodification,inheritance,oroverriding—usedforimmutablevariables,methods,andclasses;2.finallyisablockinexceptionhandlingthatalwaysexecutesaftertry-catch,ensuringcleanupcoderunsregardlessofexceptionsorearlyexits;3.finalize()

Aug 07, 2025 pm 07:22 PM

Comparing Java Web Frameworks: Spring vs. Micronaut vs. Quarkus

QuarkusandMicronautoutperformSpringinstartuptimeandresourceefficiency,especiallyincloud-nativeandserverlessenvironments.2.Springoffersthebestdeveloperexperienceduetoitsmatureecosystem,extensivetooling,andbroadcommunitysupport,thoughQuarkus’devmodewit

Aug 07, 2025 pm 06:51 PM

Advanced Java Security for Cloud Native Applications

In order to improve the security of Java applications in cloud-native environments, the following key measures need to be taken: 1. Use the principle of least permissions to configure the runtime environment to avoid running containers with root users. Create non-root users in Dockerfile and set up the runAsNonRoot policy for Kubernetes; 2. Enable TLS1.2 or higher and disable unsafe protocols, and limit the encryption protocol through SpringBoot configuration or JVM parameters; 3. Control the security of the dependency library, use OWASPDependency-Check to scan for vulnerabilities and promptly upgrade third-party libraries with risks; 4. Use Secrets to manage sensitive information, avoid hard-coded passwords and keys, and it is recommended to use

Aug 07, 2025 pm 06:44 PM

cloud native java security

Building a Command-Line Application in Java with Picocli

Use Picocli to easily build powerful Java command line applications. 1. Add Picocli to the project (Maven or Gradle); 2. Use @Command, @Option and @Parameters to define commands, options and parameters; 3. Implement the Callable interface and write business logic in the call method to automatically obtain help, version, verification and other functions; 4. Support the subcommand structure through @Command's subcommands attribute, which is suitable for complex tools; 5. Bash/zsh automatic completion script can be generated to improve the user experience. In the end, you can convert the Java class into a professional-level CLI tool with just a few lines of annotations.

Aug 07, 2025 pm 06:08 PM

How is the this keyword used within a Java class?

ThethiskeywordinJavareferstothecurrentinstanceofaclassandisusedtoresolvevariablenamingconflicts,asshownwhendistinguishinginstancevariablesfromparameters;2.Itenablesconstructorchainingbycallinganotherconstructorinthesameclassusingthis(),whichmustbethe

Aug 07, 2025 pm 05:24 PM

How to check if a file exists in Java

UseFiles.exists(Paths.get(path))tocheckifafileexistsinJava,asitisthemodernandrecommendedapproachwithbetterhandlingofsymboliclinksandpermissions;2.Optionally,combinewithFiles.isRegularFile(),Files.isReadable(),orFiles.isWritable()toverifyfiletypeandac

Aug 07, 2025 pm 04:35 PM

java File existence