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Judgment of the validity of Java string 'binary number': From common misunderstandings to efficient practices
This tutorial is intended to guide developers on how to accurately determine whether a Java string consists of only the characters '0' and '1' (i.e. whether it is a "binary number"). The article will first analyze the character comparison mistakes that beginners often make, revealing the key differences between (char) int and 'char' literals. Subsequently, a concise and efficient loop traversal and character range judgment scheme will be provided, and other regular expression-based optimization methods will be explored to ensure the robustness and readability of the code.
Sep 02, 2025 pm 12:27 PM
JPA column update control: In-depth understanding of updatable=false and advanced policies
This article aims to deeply explore the actual role and limitations of @Column(updatable = false) annotation in JPA/Hibernate, and provide a variety of implementation strategies for users to expect to prohibit specific column updates and throw exceptions. We will analyze the behavior of updatable=false and introduce best practices to enforce column non-updated rules through entity Setter methods, JPA lifecycle callbacks, and database-level constraints, and provide instant error feedback.
Sep 02, 2025 pm 12:24 PM
SpringBoot and Thymeleaf: Efficiently construct dynamic tables and operation buttons
This article details how to combine the Thymeleaf template engine in Spring Boot applications to display list data efficiently and correctly in HTML tables, and integrate independent operation buttons (such as deletion) for each data. By encapsulating the data model, preparing data in the controller, and using th:each in the Thymeleaf template for a single iteration, ensuring that each row of data and its corresponding operation buttons are clear and duplicated, thus building a structured and fully functional dynamic table.
Sep 02, 2025 pm 12:12 PM
How to write a program to prompt the user to re-enter the number within the valid range
This article aims to guide beginners to write a program that can receive numbers entered by users and determine whether the number is between 30 and 70. If the number is out of range, the program prompts the user to re-enter until a valid number is entered. We will explain the code implementation in detail and provide necessary precautions to help readers understand loop control and input and output operations.
Sep 02, 2025 pm 12:03 PM
Correct way to access private variables of parent class through subclasses (Java)
This article aims to explore how a child class accesses the private variables of the parent class in Java when modification is not allowed. The core method is to use the public methods provided by the parent class (such as toString()) or use method rewriting combined with the super keyword to indirectly access and extend information. The article will explain the specific implementation in detail through sample code and emphasize design principles and best practices.
Sep 02, 2025 am 11:36 AM
Android RecyclerView interacts with Activity: Using interface callback mechanism
This article discusses how to safely and effectively realize the communication between RecyclerView and Activity in Android development to solve the problem of directly calling the MainActivity method from the RecyclerView click event causing NullPointerException. By introducing an interface callback mechanism, RecyclerView can send event notifications to the Activity and pass data, allowing the Activity to update the UI in the main thread, avoiding incorrect Activity instantiation and view uninitialization issues.
Sep 02, 2025 am 11:33 AM
Implementing PIN code input box in Codename One: the correct combination of numbers and password masks
This article explains in detail how to correctly set digital input and password mask for PIN input box in Codename One. By parsing the setConstraint mechanism of TextComponent, common chain call misunderstandings are corrected, and it is pointed out that bits or operators | should be used to combine TextArea.NUMERIC and TextArea.PASSWORD to ensure that the input box meets both the numerical limits and password hiding requirements.
Sep 02, 2025 am 11:30 AM
Java: How can a child class indirectly utilize the parent class private members by overwriting methods without modifying the parent class
In Java, direct access is not allowed when a subclass needs to use the private members of the parent class without modifying the parent class. This tutorial will show how to indirectly utilize the processed private data inside the parent class by calling the public or protected method of the parent class (such as super.toString()), especially for scenarios where methods are overridden and functions are extended based on this.
Sep 02, 2025 am 11:27 AM
Integrating EJB and JAX-WS in WildFly: Solving deployment and access difficulties
This article details the practice of integrating EJB (Enterprise JavaBeans) and JAX-WS (Java API for XML Web Services) projects into EAR (Enterprise Archive) on WildFly application server. The tutorial covers multi-module Maven project structure, dependency management, and how to solve common NoClassDefFoundError class loading problems during deployment, and guides readers to correctly access the WSDL definition of deployed web services.
Sep 02, 2025 am 11:15 AM
Java date and time string conversion practice: from multiple formats to 'dd.MM.uuuuu'
This article explores in-depth conversion of datetime strings in different formats (such as RFC 1123 and standard datetime) to a unified "dd.MM.uuuu" format in Java. The tutorial focuses on the use of the java.time API, including the pattern symbols of DateTimeFormatter, the importance of Locale, and how to parse and final formats for different input formats, avoiding the common pitfalls of older versions of SimpleDateFormat, and providing detailed code examples and best practices.
Sep 02, 2025 am 10:48 AM
Resolve Spring REST API 406 Not Acceptable Error
This article aims to help developers resolve the "406 Not Acceptable" error encountered when using the Spring REST API. This error usually means that the server cannot find the representation acceptable to the client. We will introduce the causes and solutions for the error in detail, and demonstrate through sample code how to configure the producers attribute to specify the response type of the API to ensure that the client can receive and process data correctly.
Sep 02, 2025 am 10:39 AM
The correct configuration method for single-line refresh by Eclipse console\r carriage return character
This article aims to solve the problem that Java System.out.print("\r" message) cannot achieve single-line override refresh in the Eclipse console, which leads to new row output. The core solution is to configure Eclipse console preferences, enable the "Interpret Carriage Return (\r) as control character" option, and ensure that the \r character is correctly parsed into a carriage return operation rather than a normal character, thus achieving the expected single-line update effect of the console.
Sep 02, 2025 am 10:33 AM
Java Tutorial: Efficiently verify whether strings contain only '0' and '1' (dual number verification)
This article aims to guide Java developers to efficiently and accurately determine whether a string consists of only characters '0' and '1' (i.e., "dual" strings). We will dig into common programming pitfalls such as loop boundary errors and comparison problems caused by confusion of characters with ASCII values, and provide a concise and robust solution to help developers write more reliable string verification logic.
Sep 02, 2025 am 10:30 AM
Verify method calls inside Executor.execute using Mockito
This article aims to resolve threading issues encountered when using Mockito to validate methods called internally by the Executor.execute method. By using SynchronousExecutor, you can ensure that the code executes synchronously, allowing Mockito to correctly verify method calls. This article will provide detailed steps and sample code to help you effectively test asynchronously executed code.
Sep 02, 2025 am 10:27 AM
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