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Value-based sorting: Solve the problem of key-value conflict in TreeMap

This article explores the problem of data loss due to Comparator treating different keys as equal when sorting Java TreeMaps based on values ??using a custom Comparator. We will analyze the cause of the problem and provide solutions to ensure that all key-value pairs are properly retained in the sorted map. At the same time, we will also notice the potential risks of null pointer exceptions and provide a safer Comparator implementation.

Aug 25, 2025 am 09:54 AM

Solve the problem of Selenium Chromedriver path recognition in IntelliJ

This article aims to solve the common IllegalStateException when running Selenium tests in IntelliJ IDEA, that is, the system cannot find the ChromeDriver driver path. Although the user may have set the webdriver.chrome.driver system properties correctly, the error persists. The core solution is to ensure that all necessary Selenium library files (including the JAR packages in the lib subdirectory and their parent directory) are correctly added to the IntelliJ project's module dependencies, thereby solving driver loading failures caused by incomplete classpath configuration.

Aug 25, 2025 am 09:51 AM

OptaPlanner Overconstraint Planning: Understanding and applying virtual value policies

This article explores two core strategies of OptaPlanner when dealing with overconstrained planning scenarios: utilizing nullable=true and introducing "virtual values". We will analyze the working principles, applicable scenarios, configuration methods and constraint design of these two methods in detail, aiming to help developers effectively solve the problem of insufficient resources according to actual business needs and achieve optimal or suboptimal planning results.

Aug 25, 2025 am 09:45 AM

Detailed explanation of Micronaut declarative client exception handling configuration

This article details how to use the exceptionOnErrorStatus configuration item in Micronaut declarative client and explains its behavior differences in different scenarios. Through instance code and test cases, we explain how to correctly configure and handle exceptions of declarative clients, avoid common misunderstandings and errors, and help developers better understand and use Micronaut's declarative client functions.

Aug 25, 2025 am 09:39 AM

Java merge sorting: Solve the limit on the number of sorting elements and the optimization of code style

This article aims to solve the problem of limiting the number of sorting elements that occur in Java merge sorting, and provides suggestions for code style optimization. By analyzing the problem code, pointing out that the reason for the error is that the wrong list operation is used during the merging process and providing the correct code implementation. In addition, this article also emphasizes the importance of interface-oriented programming in Java programming and provides corresponding modification suggestions to improve the maintainability and scalability of the code.

Aug 25, 2025 am 09:33 AM

Convert floating point numbers to strings without rounding

This article introduces solutions to convert float type numerical values ??to String types in Java while avoiding the scientific notation and rounding problems. Due to the accuracy limitations of float type, direct conversion may lead to accuracy loss. The article explains the principle of float type storage in detail, and recommends the use of double type or BigDecimal class to ensure accuracy, and provides sample code for demonstration.

Aug 25, 2025 am 09:30 AM

Javax Bean Validation: In-depth exploration of collection (List) element validation

This article explores in-depth mechanisms for validating elements inside List collections using Javax Bean Validation in Java. By introducing the correct application of type annotations and @Valid annotations, combined with the appropriate Hibernate Validator version, we can achieve accurate verification of each element in the collection (such as the mailbox format) to ensure data integrity and consistency.

Aug 25, 2025 am 09:18 AM

What is a ClassNotFoundException in Java?

ClassNotFoundExceptionoccurswhentheJVMcannotfindaspecifiedclassatruntime;commoncausesincludeincorrectclassnames,missingJARfiles,classpathissues,orfaileddynamicloading;typicalscenariosinvolveloadingdatabasedriversorreflection-basedinstantiation;tofix,

Aug 25, 2025 am 09:18 AM

java

Calculate the number of possible paths to the questionnaire: Java recursive implementation

This document is intended to guide developers how to use Java recursive algorithms to calculate the number of all possible paths in a survey. We will use an actual JSON structure example to explain in detail how to use recursive methods to traverse various branches of the questionnaire and finally count all possible completion paths. This document will provide code examples and detailed explanations to help developers understand and apply this method.

Aug 25, 2025 am 08:27 AM

What is the this keyword in Java?

ThethiskeywordinJavareferstothecurrentobjectinstanceandisusedtoaccessinstancevariables,invokeconstructors,passthecurrentobjectasaparameter,returnthecurrentobject,andresolvemethodcallambiguity.Ithelpsdistinguishbetweeninstancevariablesandparameterswit

Aug 25, 2025 am 08:20 AM

Get the correct posture for the current object instance: this pass in Java Supplier

This article explores how to pass the current object instance (this) to Supplier in the most efficient way in Java 8, especially when using the completeAsync method of java.util.concurrent.CompletableFuture. The article analyzes the different ways of using Lambda expressions and method references and discusses their performance differences, aiming to help developers choose the most appropriate solution.

Aug 25, 2025 am 07:45 AM

How to execute a SQL query in Java

To execute SQL query, you need to use JDBC. The steps are as follows: 1. Load the JDBC driver (modern version can be omitted); 2. Establish a database connection through DriverManager.getConnection; 3. Use Statement or PreparedStatement to execute query, use executeQuery with SELECT, add, delete and change to executeUpdate, and query with parameters. PreparedStatement is recommended to prevent SQL injection; 4. Use try-with-resources to automatically close the Connection, Statement and ResultSet resources to avoid memory

Aug 25, 2025 am 07:40 AM

Tutorial on calculating the percentage of string words in Java

This tutorial details how to efficiently and accurately calculate the percentage of user input strings that meet specific patterns (such as pure letter words, starting with capital letters) in Java. The content covers secure input processing, storing data with arrays, pattern matching using regular expressions, and writing reusable counting logic, aiming to help developers build robust string analysis programs.

Aug 25, 2025 am 06:45 AM

Efficiently compare specific properties of different lists in Java: Optimize search using HashMap

This article aims to introduce an efficient method for comparing specific properties of two different lists in Java. By converting one of the lists to a HashMap, taking the property value as the key and the object itself as the value, the number of iterations can be significantly reduced, thus optimizing the performance of the comparison operation. This article will explain in detail how to achieve this with HashMap and provide sample code and considerations.

Aug 25, 2025 am 06:42 AM