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What is the diamond problem in Java?

Thediamondproblemoccurswhenaclassinheritsfromtwoparentclassesthatbothinheritfromthesamegrandparentclass,causingambiguityinmethodresolution.1.Javaavoidsthisbynotallowingmultipleinheritanceofclasses.2.However,Javaallowsimplementingmultipleinterfaceswit

Jul 11, 2025 am 01:51 AM

What is a JWT and how to use it in a Java application?

The use of JWT in Java applications involves generation, parsing and verification of tokens, and its core is implemented through dependency libraries such as auth0/java-jwt. 1. Add Maven dependencies to introduce the java-jwt library; 2. Use the HMAC256 algorithm and key to generate a token containing the topic and declaration; 3. Build a validator to parse and verify the token signature; 4. Extract the declaration from the payload for permission judgment. In actual applications, it is necessary to safely store keys, enable HTTPS transmission, set the token expiration time, and integrate it with SpringSecurity to ensure the security and flexibility of authentication and authorization.

Jul 11, 2025 am 01:45 AM

java jwt

How to produce and consume messages from Apache Kafka with Java?

The key to producing and consuming ApacheKafka messages using Java is to properly configure the Producer and Consumer APIs and understand their basic processes. 1. First add Kafka client dependencies to ensure that the version is compatible with the cluster; 2. When writing producers, configure bootstrap.servers, key.serializer and value.serializer, and create a KafkaProducer instance to send messages, pay attention to closing resources and optional callback processing; 3. When writing consumers, configure group.id, deserializer, etc., use KafkaConsumer to subscribe to topics and loop to pull messages, pay attention to submitting offset

Jul 11, 2025 am 01:43 AM

java kafka

Java multithreading tutorial

The key to Java multi-threading programming is to understand thread creation, synchronization mechanism and resource management. 1. Threads are the basic unit of program execution. They can be created by implementing the Runnable interface or inheriting the Thread class; 2. Synchronized, wait/notify or ReentrantLock are required to control the execution order; 3. Avoid deadlocks, unified resource application order, set timeouts and reduce nested locks; 4. Using thread pools can improve performance. It is recommended that ExecutorService manage fixed, single-thread or cache pools. Mastering these core points can effectively deal with concurrent scenarios.

Jul 11, 2025 am 01:39 AM

Testing Java Code Effectively with JUnit Framework

JUnit is the preferred framework for Java unit testing because of its simplicity, stability and extensive integration. Using JUnit can improve code quality, especially when modifying or extending features. To start writing the first test, you need to: 1. Add dependencies; 2. Create a test class and end with Test; 3. Use the @Test annotation method and write assertions. Practical testing should: cover core logic, maintain independence, use Setup/Teardown, and test exception behavior. Test coverage cannot be ignored, but it is necessary to analyze effective paths in combination with tools such as JaCoCo and connect to CI to ensure continuous integration.

Jul 11, 2025 am 01:25 AM

Exploring New Features Introduced in Java 8

The core new features of Java8 include Lambda expressions, StreamAPI, and default methods. 1. Lambda expressions simplify the implementation of functional interfaces, making the code more concise, but it should be noted that it is only applicable to functional interfaces and should not be too complicated; 2. StreamAPI provides declarative data processing methods to improve collection operation efficiency, but should avoid using them on small amounts of data and reduce side effects; 3. The default method allows interfaces to define methods to implement, enhance backward compatibility, but cannot access class state and need to solve method conflict problems. The rational use of these features can improve code quality and development efficiency.

Jul 11, 2025 am 01:24 AM

java java 8

Handling Null Pointer Exceptions Safely in Java

The key to dealing with null pointer exceptions lies in prevention and reasonable response. 1. Understand the root cause of NullPointerException, such as accessing properties or methods of null objects, obtaining null array length, etc.; 2. Use the Optional class to elegantly process values ??that may be null, such as ofNullable, ifPresent, orElse, etc.; 3. Make good use of conditional judgments and tool classes for defensive programming, such as manually null, using Objects.requireNonNull(), StringUtils.isNotBlank(), etc.; 4. Follow practical suggestions in daily development, such as not assuming that variables have values, clarifying that interface null is legal

Jul 11, 2025 am 01:22 AM

java Null pointer exception

What is Project Reactor and reactive programming in Java?

ReactiveprogramminginJavaisaparadigmforhandlingasynchronousdatastreamsefficiently.Itusesnon-blockingoperationsandbackpressuretomanagehighconcurrencyandreal-timeinteractions.ProjectReactorprovideskeytoolslikeFlux(formultipleitems)andMono(forzerooronei

Jul 11, 2025 am 12:38 AM

reactive programming

Java lambda expressions tutorial

LambdaexpressionsinJavaareinlinefunctionsusedwithfunctionalinterfacestomakecodecleaner.IntroducedinJava8,theyallowtreatingfunctionalityasamethodargument.Theysimplifytaskslikesorting,filtering,andeventhandling.Tousethem,matchthelambdatoafunctionalinte

Jul 11, 2025 am 12:36 AM

java

How to check if a number is prime in Java?

TocheckifanumberisprimeinJava,thecoremethodinvolvestestingdivisibilityuptothesquarerootofthenumber.1.First,handleedgecases:numberslessthanorequalto1arenotprime,2isprime,andevennumbersgreaterthan2arenotprime.2.Usealoopstartingfrom3uptothesquarerootoft

Jul 11, 2025 am 12:32 AM

java prime numbers

Implement a binary search tree in Java

To implement the binary search tree (BST) in Java, first define the node class, then create the BST class management tree structure, and then implement the insertion and search logic. 1. Define the Node class, including values ??and left and right child nodes; 2. Create the BinarySearchTree class and set the root node; 3. Implement the insert method, find the correct position through recursion and insert a new node; 4. Add a search method, and find the target value recursively according to the size comparison; 5. Optionally implement inorder and other traversal methods to verify the tree structure. The above steps constitute a BST with basic insertion, search and traversal functions.

Jul 11, 2025 am 12:08 AM

java binary search tree

Best practices for using Java Optional

Java's Optional should be used correctly to avoid increasing code complexity. 1. Do not wrap null with Optional.ofNullable() should be used to process values ??that may be null; 2. Avoid using Optional in entity classes or collections, because it increases memory overhead and serialization is prone to problems; 3. Use orElse and orElseGet correctly, and use orElseGet first when the default value is high at a high cost; 4. Try to avoid calling get() directly, and it is recommended to use it in combination with ifPresent() or map()/filter() to improve security. Optional is designed to express that it is "probably not present"

Jul 10, 2025 pm 02:02 PM

Best Practices

How to create a custom exception in Java?

The key to customizing Java exceptions is to understand the inheritance structure and select the type reasonably. 1. Clear the exception type: If the caller needs to be forced to handle it, inherit Exception (checked exception); if it is a runtime error, inherit RuntimeException (non-checked exception). 2. When creating a custom exception class, you should provide no parameters, string parameters and constructors with exception reasons to ensure availability. 3. In the project, it should be reasonably thrown at business logic key points, such as login failure, verification failure, etc., and a unified response should be combined with global exception handling. At the same time, note that the detected exception needs to be declared by try-catch or throws. 4. Avoid over-customization and prioritize reusing standard exceptions such as IllegalArgumentEx

Jul 10, 2025 pm 02:02 PM

What is a local variable?

Localvariablesaredefinedwithinaspecificscopelikeafunctionorblockandcannotbeaccessedoutside.Theyhelporganizecode,preventnamingconflicts,andimprovereadabilityandmaintenance.Forexample,variableslikelengthandwidthinsideafunctiontocalculateareawon’tclashw

Jul 10, 2025 pm 01:55 PM