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How to run a Java program from the command line

EnsureJDKisinstalledandverifywithjava-versionandjavac-version.2.CreateaJavafilenamedHelloWorld.javawithamatchingclassnameandcorrectmainmethod.3.CompileusingjavacHelloWorld.javatogeneratethe.classfile.4.RuntheprogramwithjavaHelloWorld,ensuringcorrectc

Sep 06, 2025 am 02:22 AM

How to use an interface in Java

Definetheinterfaceusingtheinterfacekeyword,declaringabstractmethodslikestart(),stop(),andgetSpeed()inDrivable;2.Implementtheinterfaceinaclasswiththeimplementskeyword,providingconcreteimplementationsforallabstractmethods,asCardoesforDrivable;3.Usethei

Sep 06, 2025 am 01:37 AM

Deep parsing and best practices for JavaFX nested controller injection

This article explores in-depth common problems that cause NullPointerException by failing injection of nested controllers in JavaFX. The core reason is that the fx:id does not match the controller field naming rules. By analyzing the FXML loading mechanism in detail, the article provides a solution that complies with the Java naming specifications, and emphasizes the conventional naming pattern between fx:id and associated controller fields, aiming to help developers build clear-cut and maintainable JavaFX componentized applications.

Sep 05, 2025 pm 12:57 PM

Solve the Android calculator application crash problem: string parsing and null value processing

This article aims to help developers solve the crash problem caused by string parsing in Android calculator applications. By checking the null value of the result displayed on the calculator screen and handling it appropriately, the exceptions raised by the Double.parseDouble() method when parsing an empty string can be avoided, thereby improving the stability of the application and user experience. This article will provide detailed solutions and code examples to help you build more robust Android calculator applications.

Sep 05, 2025 pm 12:51 PM

How to prevent RecyclerView from refreshing all data when adding new data

This article describes how to use the DiffUtil class to optimize data updates for RecyclerView to avoid refreshing the entire list when new data is added, thereby improving performance and user experience. By implementing a custom DiffUtil.Callback, you can accurately calculate the differences between old and new datasets and update only the view items that need to be changed.

Sep 05, 2025 pm 12:48 PM

MapStruct Advanced Application: Map Foreign Key IDs in DTO to Associated Entity Objects

This tutorial explains in detail how to correctly map the ID field in the Data Transfer Object (DTO) that represents a foreign key to the corresponding ManyToOne associated entity in the entity object when using MapStruct for object mapping. By converting the MapStruct mapper to an abstract class and injecting Repository, a custom parsing method is implemented to ensure that the foreign key ID can be effectively converted into a complete associated entity object, thus solving the problem that the default map cannot handle ID-to-entity conversion.

Sep 05, 2025 pm 12:45 PM

Solve the time area issue when Java Mail sends iCalendar invitation

This article aims to solve the problem of meeting time deviation due to improper time zone setting when sending iCalendar conference invitations using Java Mail. By analyzing the definition of time format in the iCalendar specification and providing sample code for processing time zones using the ZonedDateTime class, we help developers correctly set the time in the meeting invitation, avoid time deviations, and ensure the accuracy of the meeting invitation.

Sep 05, 2025 pm 12:36 PM

Problem handling spaces when reading a single character from Scanner

This article aims to solve the problem that occurs when reading a single character when using Scanner to read user input in Java because Scanner uses spaces as delimiters by default. We will dig into how Scanner works and provide solutions to solve this problem by using the Scanner.nextLine() method to read the whole line input, ensuring that the program can correctly handle input containing spaces.

Sep 05, 2025 pm 12:30 PM

Java Swing implements logic gates with check boxes and images

This article will guide you to create a simple GUI program using Java Swing to simulate an AND logic gate. The program contains two check boxes and a label. When both check boxes are selected, the label will be displayed in green; otherwise, it will be displayed in red. We will update the display of the tag dynamically by listening to the status change event of the checkbox. This article provides complete code examples and discusses how to use images instead of simple text tags.

Sep 05, 2025 pm 12:27 PM

Implement universal enum type verification in Spring Boot

This article describes how to implement universal enum type validation using custom annotations in Spring Boot projects. Through the Java reflection mechanism, a common verification annotation can be created that can receive an enumeration type as a parameter to verify that the input value is a valid value of the specified enumeration type. This article will provide specific code examples and steps to help developers easily implement this feature.

Sep 05, 2025 pm 12:24 PM

Deeply understand the 'Future' state and its processing strategies in Flyway migration

When the Flyway migration script is modified after successful execution, it will cause a checksum mismatch, which will cause the migration script to enter the "Future" state, preventing the execution of subsequent new migrations. This article will deeply analyze the causes of the "Future" state in Flyway and its impact on the migration process, and provide specific operational steps to solve this problem in the development environment. At the same time, it emphasizes best practices for Flyway script management in production environments to ensure the integrity and stability of database version control.

Sep 05, 2025 pm 12:18 PM

List of words based on frequency sorting: Java Tutorial

This tutorial shows how to sort a list of words of a string type based on a frequency list of another integer type. We will use Java 8's Stream API and Comparator interface to implement an efficient and concise sorting method to ensure that the index relationship between word list and frequency list remains consistent after sorting.

Sep 05, 2025 pm 12:15 PM

Node.js spawn command parameter analysis and shell: true application

This article discusses common problems encountered by the Node.js child_process.spawn function when dealing with complex command line parameters, especially when parameters contain paths or require special explanations, which may cause target programs (such as Java) to be unrecognized correctly. This type of problem can be effectively solved by introducing the shell: true option and combining correct parameter formatting, while highlighting safety precautions when using this option.

Sep 05, 2025 pm 12:06 PM

Tutorial for efficiently extracting words with specified length in strings in Java

This article details how to efficiently extract words of a specified length from an input string in Java. By using the String.split() method combined with the filter() and toArray() operations of the Java Stream API, this function can be implemented concisely and elegantly, avoiding complex loops and manual index management, and improving the readability and maintenance of the code.

Sep 05, 2025 pm 12:03 PM