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ISBN Format Output: Java Implementation Guide

This article describes how to format output ISBN (International Standard Book Number) using Java. The String.substring() method and the System.out.printf() function enable the input 9-digit string to be formatted into standard ISBN format and output "X" or numbers correctly based on the value of the check bit. At the same time, this article also emphasizes the importance of input verification to ensure that the program can handle various input situations correctly.

Aug 27, 2025 am 01:54 AM

How to connect to a MySQL database with JDBC

To connect to the MySQL database, you need to follow the following steps: 1. Add the MySQLJDBC driver, introduce the mysql-connector-j dependency through Maven and Gradle, or manually download the JAR package and add the classpath; 2. Modern JDBC versions do not need to explicitly load the driver, Class.forName("com.mysql.cj.jdbc.Driver") can be omitted; 3. Use the DriverManager.getConnection() method to pass in the URL format "jdbc:mysql://host:port/dbname? parameter"

Aug 27, 2025 am 01:45 AM

Year Error when adding dates in Oracle Database using SQL: Causes and Solutions

This article conducts an in-depth analysis of year errors caused by improper date formatting when using SQL statements to update dates in Oracle databases. The article explains the potential pitfalls of RRRR date format in detail and provides best practices to avoid such problems, including directly using sysdate for date addition and subtraction, and using the trunc() function to remove the time part to ensure the accuracy of date updates.

Aug 27, 2025 am 01:42 AM

How to convert a char array to a string in Java?

To convert a char array to a string, use the String constructor. 1. Use newString(charArray) to convert the character array directly into a string, such as char[]charArray={'h','e','l','l','o'};Stringstr=newString(charArray); output hello; 2. This operation will copy the content of the array, so subsequent modification of the original array will not affect the string; 3. You can also use String.valueOf(charArray), the effect is the same as the constructor; 4. If you need to convert subarrays, you can use newString(chars, offset

Aug 27, 2025 am 01:01 AM

Tutorial on sorting and searching List of Lists by specified columns in Java

This tutorial details how to process List data structures in Java to achieve sorting by specified "columns" and efficiently find "rows" containing specific values ??on this basis. The article compares and sorts row data through custom Comparator and provides strategies to identify target column indexes, thus solving common challenges in organizing and retrieving data in complex nested lists.

Aug 26, 2025 pm 12:27 PM

Spring Webflux vs. Kotlin: Correct execution of CRUD operations in responsive streams

This tutorial explores in-depth how to perform CRUD operations inside Mono or Flux subscriptions when developing responsive applications using Spring Webflux and Kotlin, which can cause data to not be persisted. The core is to understand the non-blocking nature of responsive programming and emphasize that side-effect operations should be avoided in subscribe callbacks. By comparing error examples and correct practices, the article explains in detail how to seamlessly integrate database operations into data streams using responsive operators such as flatMap to ensure that data persistence is consistent with responsive principles.

Aug 26, 2025 pm 12:18 PM

Gradle Multi-module Project Dependency Configuration Guide: Solving Subproject Dependency Issues

This article aims to help developers solve the problem of failure in sub-project dependencies in Gradle multi-module project construction. With detailed code examples and configuration instructions, we will dive into how to properly configure the settings.gradle file and how to declare project dependencies in the build.gradle file of the subproject, ensuring that Gradle correctly parses and builds multi-module projects.

Aug 26, 2025 pm 12:15 PM

Java Caesar password implementation: How to properly ensure spaces in text

This tutorial discusses in detail how to solve the problem of missing spaces in encrypted output when implementing Caesar passwords in Java. By analyzing common encoding errors, i.e. skipping space characters incorrectly, this article provides a modified code example that shows how to ensure that spaces are preserved during the encryption process, thereby generating more expected encrypted text. The tutorial further discusses the importance of matching character set definitions with modulo operations to help developers build more robust implementations of Caesar ciphers.

Aug 26, 2025 pm 12:09 PM

Solutions to the limitation of this reference in Java constructor and circular dependency between objects

In Java, the subclass constructor cannot refer to this before calling super() because the object has not been fully initialized at this time, especially the parent class part and final fields may not be assigned. When inter-object cyclic dependencies occur in the design, especially in the final field, it will cause a compilation error of "Cannot reference 'this' before supertype constructor has been called". Solving this problem usually requires tweaking the design, such as setting one of the circular dependencies fields to non-final and initializing after the super() call is completed, or using more flexible object creation such as builder pattern.

Aug 26, 2025 am 11:51 AM

Java Swing: The correct way to convert JRadioButton to string

In Java Swing applications, when you need to get the user selected text from the JRadioButton group, calling ButtonGroup.getSelection().toString() directly will usually get a useless object hash value. This article will explain in detail how to correctly convert the JRadioButton's selected items into meaningful strings. The core is to use the JRadioButton's setActionCommand() method to associate it with a string command, and obtain this customized string through the ButtonModel's getActionCommand() method to achieve accurate data acquisition.

Aug 26, 2025 am 11:45 AM

Solve the issue of JNA loading failure during Spring Boot image build

This article aims to help developers resolve the "Can't load library" error encountered on an M1 Mac when building a Docker image using Spring Boot, which is usually related to failed loading of the JNA (Java Native Access) library. This problem can be effectively resolved by adjusting the version compatibility of Spring Boot, Spring Cloud, and Java, ensuring smooth image building.

Aug 26, 2025 am 11:39 AM

Complete tutorial on building a Dockerfile with Testcontainers

This document is intended to guide developers on how to integrate Testcontainers during Dockerfile builds to solve the problem of running test cases that depend on Docker environments in CI or local build environments. By leveraging the socat tool, the host's Docker socket is exposed to the build environment, allowing Testcontainers to start and manage containers during the Dockerfile build phase, thereby achieving complete integration testing.

Aug 26, 2025 am 11:36 AM

Tutorial on entering string word percentages and specific pattern recognition in Java

This tutorial details how to efficiently process a collection of strings entered by a user in Java and calculate the percentage of strings that match a specific pattern such as pure letter words or words that start with capital letters. The article focuses on the collection of inputs, the application of regular expressions, the implementation of modular counting methods, and the display of final results, aiming to help readers master the key techniques of string analysis and processing.

Aug 26, 2025 am 11:27 AM

Maestro UI test run error NoSuchMethodError Solution

This article provides a solution to the problem that the Maestro UI automation test tool has an error in java.lang.NoSuchMethodError: java.io.InputStream.readAllBytes()[B] in Flutter application test. The core of this solution is to ensure that JDK 11 is installed and configured correctly and remove other versions of JDK that may cause conflict, thereby resolving the dependency problem of Maestro runtime.

Aug 26, 2025 am 11:15 AM