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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

How to use a Java profiler like JVisualVM or JProfiler?

The key to using JavaProfiler is to understand its functionality and follow the steps. 1. Start the tool and connect to the target application. JVisualVM can run directly and automatically recognize local processes. JProfiler needs to be installed and supports remote connections. 2. Analyze CPU and memory. JProfiler provides "CallTree" and "HotSpots". JVisualVM samples CPU through "Sampler", and both can view memory trends and object allocations. 3. Position thread problems. JVisualVM checks status changes through "Threads" tag. JProfiler can detect deadlocks and display resource waiting conditions. 4. In combination with the external environment, check the problem.

Jul 10, 2025 pm 01:52 PM

What are common Java security vulnerabilities and how to prevent them?

Java security issues mainly include unsafe deserialization, SQL injection, sensitive information leakage and improper permission control. 1. Unsafe deserialization may trigger arbitrary code execution, and deserialization of untrusted data, using whitelisting mechanisms, or alternative formats such as JSON should be avoided. 2. SQL injection can be prevented through parameterized queries, precompiled statements and ORM framework. 3. Sensitive information leakage needs to be protected through log desensitization, encryption configuration, exception handling and HTTPS. 4. Improper permission control may lead to overprivileged access. Authentication, RBAC, server authentication should be enforced and unpredictable resource identifiers should be used. Developers' good coding habits and security awareness are the key to ensuring the security of Java applications.

Jul 10, 2025 pm 01:51 PM

Vulnerability prevention java security

Securing Java Applications with Spring Security Framework

The most common way to protect Java applications is to use the SpringSecurity framework, which lies in user authentication, permission control and security configuration. 1. User authentication supports forms, HTTPBasic and OAuth2. It is recommended to load user information from the database with UserDetailsService, and enable CSRF protection and verification code mechanism to enhance security; 2. Permission control is implemented through roles and permissions. Access can be restricted using @PreAuthorize annotation, and URL level restrictions can be configured through HttpSecurity to keep the role level clear and avoid confusion; 3. Security configuration should enable security headers, configure session management, and enable log auditing, and at the same time adjust potential risks carefully.

Jul 10, 2025 pm 01:50 PM

How to implement the Strategy design pattern in Java?

TheStrategydesignpatterninJavaallowsdefiningafamilyofalgorithms,encapsulatingeachone,andmakingtheminterchangeabletochangebehavioratruntime.1.Defineastrategyinterfacethatdeclaresthemethod(s)allstrategiesmustimplement.2.Implementconcretestrategiesthatp

Jul 10, 2025 pm 01:36 PM

How to create a custom collector for Java Streams?

TocreateacustomcollectorinJavaStreams,useCollector.of()withsupplier,accumulator,combiner,andfinisher.1.Supplierinitializesthecontainer.2.Accumulatoraddselementstoit.3.Combinermergescontainers,crucialforparallelstreams.4.Finisherconvertstheresulttothe

Jul 10, 2025 pm 01:34 PM

Common causes of Java NullPointerException and solutions.

NullPointerException (NPE) in Java is a common runtime exception caused by operating null references. It can be prevented by the following methods: 1. Avoid using it before initializing the object, add null checks before calling the method; 2. Document the methods that may return null and prioritize whether it is null, and use Optional classes reasonably; 3. Avoid automatic unboxing and throw exceptions, use types such as wrapper class default values ??or OptionalInt; 4. Identify the support of null by the collection, and filter null values ??before processing. The occurrence of NPE can be effectively reduced through good coding habits.

Jul 10, 2025 pm 01:33 PM

How to create an immutable class in Java?

Creating an immutable class in Java follows several key steps. 1. Declare the class as final to prevent inheritance from corruption of immutability; 2. Set all fields to privatefinal to ensure that external cannot be modified and the state remains unchanged after the object is created; 3. The setter method is not provided, only getters are retained for reading attributes; 4. Initialize all fields in the constructor and copy mutable objects deeply to avoid shallow copying problems; 5. Getter returns a copy of the mutable object instead of the original reference to prevent external modification from affecting the internal state; 6. Correctly implement equals and hashCode methods to ensure the consistency of behavior during use of container classes.

Jul 10, 2025 pm 01:27 PM

java Immutable Class