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Using Project Loom for Lightweight Concurrency in Java

ProjectLoomintroducesvirtualthreadstosolveJava’sconcurrencylimitationsbyenablinglightweight,scalablethreading.1.VirtualthreadsareJVM-managed,low-footprintthreadsthatallowmillionsofconcurrentthreadswithminimalOSresources.2.Theysimplifyhigh-concurrency

Jul 26, 2025 am 06:41 AM

java concurrent

Building Resilient Java Microservices with Resilience4j

Resilience4j improves the flexibility of Java microservices through circuit breakers, current limiting, retry and other mechanisms. 1. Use circuit breakers to prevent cascade failures and prevent requests from being sent when services fail frequently; 2. Use current limit control to control concurrent access to avoid sudden traffic overwhelming downstream services; 3. Respond to temporary errors through retry mechanisms, but avoid invalid retry and resource waste; 4. Multiple strategies can be used in combination to enhance the overall resilience of the system, but attention should be paid to the mutual influence between policies. Properly configuring these functions can significantly improve the stability and fault tolerance of distributed systems.

Jul 26, 2025 am 06:36 AM

java microservices

How to add an element to an array in Java?

Adding elements to an array in Java requires a workaround to implement because the array length is fixed. 1. Use the Arrays.copyOf method: import the Arrays tool class, define the original array and new elements, create a new array of length 1 and copy the content, and finally add new elements; 2. Create a new array and copy the content: create a new array of length 1, copy the original array content through a loop, and add new elements at the last position; 3. Use ArrayList: Use a dynamic array structure, use the .add() method to directly add elements, which is suitable for frequent modification of data; the above methods are essentially the process of "create new array, copy content, and add new values". When frequent operations, use ArrayLis should be given priority.

Jul 26, 2025 am 06:32 AM

A Deep Dive into Java's HashMap and ConcurrentHashMap

HashMapisnotthread-safeandshouldonlybeusedinsingle-threadedenvironmentsorwithexternalsynchronization,whileConcurrentHashMapisthread-safeanddesignedforconcurrentaccess.2.HashMapallowsnullkeysandvalues,whereasConcurrentHashMapthrowsNullPointerException

Jul 26, 2025 am 06:10 AM

How the Java Platform Module System (JPMS) Works

JPMSintroducesmodulesviamodule-info.javatodefinedependencies,exports,andservices.2.Itenforcesstrongencapsulationbyrestrictingaccesstonon-exportedpackages,evenifclassesarepublic.3.Themodulepathreplacestheclasspath,enablingexplicitdependencyresolutiona

Jul 26, 2025 am 05:51 AM

JPMS Java模塊

The SOLID Principles Explained for Java Developers

The single responsibility principle (SRP) requires a class to be responsible for only one function, such as separating the saving and mail sending in order processing; 2. The opening and closing principle (OCP) requires opening and closing for extensions and closing for modifications, such as adding new graphics without modifying the calculator; 3. The Richter replacement principle (LSP) requires that subclasses can replace the parent class without destroying the program, such as using independent classes to avoid behavior abnormalities caused by square inheritance rectangles; 4. The interface isolation principle (ISP) requires that clients should not rely on unwanted interfaces, such as splitting the multi-function device interface to independent printing, scanning, and fax interfaces; 5. The dependency inversion principle (DIP) requires that high-level modules do not rely on low-level modules, and both rely on abstraction, such as OrderService depends on Data

Jul 26, 2025 am 05:16 AM

java SOLID Principle

Java Persistence with JPA and Hibernate: A Complete Tutorial

JPA is the abbreviation of JavaPersistenceAPI, a standard specification for mapping Java objects to database tables, and Hibernate is one of its most popular implementations, providing object-relational mapping (ORM) functionality that can simplify database operations. 1. JPA defines standards for entity mapping and CRUD operations, allowing developers to operate databases in an object-oriented way and avoid writing a large amount of JDBC code. 2. Hibernate, as an implementation of JPA, not only supports JPA specifications, but also provides advanced features such as caching, lazy loading, and transaction management. 3. Use Maven to add hibernate-core and database driver (such as H2) dependencies and in src

Jul 26, 2025 am 05:13 AM

java

Java Security for LDAP Injection Prevention

The core measures to prevent LDAP injection vulnerabilities include: 1. Avoid direct splicing of user input; 2. Filter or escape special characters; 3. Use security library to build queries. Directly splicing user input into LDAP query statements is the main reason for the injection problem. Attackers can bypass the authentication mechanism by constructing malicious input, such as input admin)(|(password=* to manipulate query logic. Therefore, user input must be processed, and special characters such as *, (,), \, NUL can be replaced by character filtering or escape functions. In addition, it is recommended to use encapsulated classes such as ApacheCommonsLDAP, SpringSecurity, or UnboundIDLDAPSDK.

Jul 26, 2025 am 05:03 AM

Creating a Custom Java Annotation Processor

Define a custom annotation, such as @LogMethod, use @Target(ElementType.METHOD) and @Retention(RetentionPolicy.SOURCE) to ensure that it is only used on methods at compile time; 2. Create annotation processor LogMethodProcessor, inherit the AbstractProcessor, rewrite the process method to process methods marked by @LogMethod, and output the compile-time prompt through Messager; 3. By META-INF/services/javax.annotation.processing.P

Jul 26, 2025 am 04:03 AM

Understanding `ConcurrentHashMap` and its Advantages in Java

ConcurrentHashMap is a thread-safe Map implementation in Java for high concurrency scenarios. Its core advantage lies in the implementation of high-performance concurrent access through fine-grained locking and lock-free read operations. 1. It does not use full table locks. Early versions used segmented locks (lockstriping). From Java 8, it used CAS operations and locked a single bucket. It only locked specific buckets or red-black tree nodes when necessary to avoid global blocking. 2. Multiple threads can read different key-value pairs at the same time. The read operation has no locks and ensures visibility based on volatile. The write operation only locks the corresponding bucket, which significantly improves concurrency throughput. 3. Provide weak consistency iterator, and ConcurrentModificationE will not be thrown during traversal.

Jul 26, 2025 am 03:53 AM

Pattern Matching for `instanceof` in Modern Java

Java14 introduces the pattern matching of instanceof as a preview feature, allowing type variables to be declared and automatically converted while type checking; 2. Pattern matching is implemented through the if (objinstanceofTypevariable) syntax, and variables are only valid in scope with the condition true and do not require casting; 3. This feature improves the readability and security of the code, reduces boilerplate code, and avoids the risk of ClassCastException; 4. When using it, pay attention to variable scope and naming conflicts, and cannot mask existing external variables; 5. Since Java16, instanceof pattern matching has become a formal standard function, which is widely applicable to the equals party.

Jul 26, 2025 am 03:37 AM

java

Java Performance Profiling with JFR and JMC

To locate performance bottlenecks in Java applications, you can use a combination of JFR and JMC tools. 1. Ensure that the JDK version supports and enables JFR; 2. Record data dynamically through the command line or runtime; 3. Use JMC to analyze key indicators such as CPU, memory, GC and hotspot methods; 4. Use events and method calls to find specific bottlenecks, such as FullGC, thread blocking or I/O problems; 5. Pay attention to setting the recording time reasonably, avoiding long-term opening, and understand interface and function limitations.

Jul 26, 2025 am 03:32 AM

java JFR

The Ultimate Guide to Java Reflection API

JavaReflection API allows programs to dynamically obtain class information and operate fields, methods, and constructors at runtime, and supports creating instances, calling methods and accessing private members; 2. Three ways to obtain Class objects are: class name.class, object.getClass(), and Class.forName("fullly qualified name"), and the third type needs to handle ClassNotFoundException; 3. Fields can be obtained through getDeclaredField() and getField(), setAccessible(true) breaks through access restrictions, and cooperates with get() and set() operation values;

Jul 26, 2025 am 03:02 AM

The Performance Impact of Java Lambda Expressions

Javalambdaexpressionstypicallydonotincuraperformancecostandoftenperformbetterthananonymousclasses.1.Statelesslambdasareimplementedassingletons,reducingmemoryoverheadandclass-loadingcostscomparedtoanonymousclasses,whichgenerateseparate.classfilesandob

Jul 26, 2025 am 02:23 AM