Article Tags
Article Tags
How to use the for-each loop in Java? (Syntax and Example)
Java's for-each loop is used to simplify traversal of arrays and collections. The syntax is for(Typeelement:collectionOrArray). It supports reading but does not support modifying structures, obtaining indexes, deleting elements, or reverse traversal.
Jan 01, 2026 am 04:17 AM
Retrofit2 dynamic token update strategy: solving the problem of continued use of old tokens
This tutorial explores the issue of continued use of old tokens due to static instances or improper management when handling API authentication token expiration with Retrofit2 and OkHttpClient. The article analyzes the root cause of the problem and provides three effective solutions, including rebuilding instances for each request, dynamic management of client instances, and cache-based conditional update strategies, aiming to help developers implement a more flexible and reliable token management mechanism.
Jan 01, 2026 am 04:15 AM
Creation and management of Apache Pulsar partition topics
This article details the two main methods of creating partitioned topics in Apache Pulsar: automatic partitioned topic creation by configuring the Broker, and manual creation of partitioned topics using the Pulsar Admin API. It is emphasized that the partition topic must be specified at the time of creation. Once a topic is created as a non-partition type, it cannot be subsequently converted to a partition topic. This is crucial for system design and planning.
Jan 01, 2026 am 04:12 AM
Maven multi-module project dependency build order management: use the -am parameter
This tutorial details how to ensure that local module dependencies with non-parent-child relationships are correctly built before the main project in a Maven multi-module project. By explaining the mvn clean install -pl -am command and its core parameter -am (also make), we will demonstrate how to use Maven's reactor mechanism to efficiently manage the build sequence of complex dependencies and ensure smooth compilation and packaging of the project.
Jan 01, 2026 am 03:33 AM
How to sort an ArrayList in Java? (Collections.sort Guide)
UseCollections.sort()tosortArrayListsin-place:forComparabletypes(e.g.,String,Integer)itusesnaturalordering;forcustomorder,passaComparatorvialambda,methodreference,orCollections.reverseOrder();topreserveoriginal,copyfirstoruseStream.sorted().
Jan 01, 2026 am 03:33 AM
How to Generate a Random Number in Java? (Code Example)
The most commonly used methods for generating random numbers in Java are java.util.Random and ThreadLocalRandom; Random is suitable for single-threaded scenarios. nextInt(bound) generates integers from 0 to bound-1, and nextDouble() returns a double of [0.0,1.0); use nextInt(max-min 1) min to customize the range [min,max]; ThreadLocalRandom.current().nextInt(min,max) is recommended for multi-threading 1); Math.random() is only suitable for simple temporary use.
Jan 01, 2026 am 03:24 AM
Solve the problem that the @NotEmpty annotation fails when the List collection contains null elements
When a List collection contains null elements, the standard @NotEmpty annotation cannot recognize it as an invalid state because it only checks whether the collection itself is null or empty. To solve this problem, you need to create custom validation annotations and corresponding validators to implement null value checking on the internal elements of the List collection, thereby ensuring data integrity and returning the expected 400 Bad Request response.
Jan 01, 2026 am 03:12 AM
How to use a for-each loop in Java? (with Examples)
Java's for-each loop is used to simplify traversing arrays and Iterable collections. The syntax is for(Typevar:collectionOrArray). It supports reading but does not support modifying elements, obtaining indexes, or concurrent modifications.
Jan 01, 2026 am 02:47 AM
How to use the Collections Framework in Java?
Java's CollectionsFramework provides a unified architecture to operate object collections. The core interfaces include List (ordered and repeatable), Set (unordered and unique), Queue (storage before processing) and Map (key-value pairs). 2. Use generic declaration collections to ensure type safety, such as ArrayList, HashSet, and HashMap. 3. By enhancing the for loop or iterator to traverse the data, you can also use forEach combined with lambda expressions. 4. Use the Collections tool class to sort, reverse or obtain immutable views to improve code readability and performance. You should choose the appropriate implementation according to your needs and give priority to using generics.
Jan 01, 2026 am 02:33 AM
Spring Security custom JSON authentication failure response
This article details how to customize the authentication entry point (AuthenticationEntryPoint) in Spring Security to return a formatted JSON error response instead of the default HTML page when the user accesses protected resources without authentication. By configuring CustomAuthenticationEntryPoint and writing JSON data directly to HttpServletResponse, developers can provide API clients with a more friendly and consistent error handling mechanism.
Jan 01, 2026 am 02:24 AM
How to remove an element from an ArrayList in Java? (by index and value)
JavaArrayList provides remove(int) to remove and return elements by index, remove(Object) to remove the first matching item by value, and removeIf() to remove all matching items. Iterator.remove() or removeIf() must be used during iteration to avoid skipping elements.
Jan 01, 2026 am 02:22 AM
How to convert a long to an int in Java? (with Type Casting)
Converting long to int in Java requires explicit cast conversion. Because the range of long (64 bits) is larger than that of int (32 bits), direct conversion will truncate the upper 32 bits and may cause silent overflow. The safe way is to use Math.toIntExact() or check the range first.
Jan 01, 2026 am 02:06 AM
How to remove an element from an ArrayList in Java? (By Index & Object)
There are two ways to delete elements from ArrayList in Java: by index and by object: remove(intindex) deletes by position and returns the element, remove(Objecto) deletes the first matching item by value and returns a Boolean value; Iterator.remove() must be used to avoid ConcurrentModificationException when traversing; both have O(n) time complexity.
Jan 01, 2026 am 02:04 AM
A practical guide to efficiently sending Java application logs to the ELK Stack
This article aims to guide developers on how to send logs generated by Java applications (based on Spring Boot and slf4j) directly from Docker containers to ELK Stack (Elasticsearch, Logstash, Kibana). We will explore the best practices for using Filebeat as a log collector to avoid local file storage and achieve efficient log transmission and analysis.
Jan 01, 2026 am 02:00 AM
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