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What are the standard ways to compare objects in Java?

In Java, the correct way of object comparison depends on the definition of "equality". 1. Use == to determine whether the reference points to the same memory object, which is suitable for reference equality or basic type value comparison; 2. Rewrite the equals() method to achieve equal content, and follow reflexive, symmetry, pass-through, consistency and non-null rules, and ensure logical equality in custom classes; 3. Rewrite hashCode() to ensure that equal objects have the same hash value to avoid problems in collections such as HashMap; 4. Implement the Comparable interface to define natural sorting, or use Comparator to achieve flexible external sorting; 5. For cases where arrays or nested objects are included, use Arrays.equals(

Aug 22, 2025 pm 01:47 PM

java object Object comparison

Doctor-Efficient Data Model and Safety Practice of Patient Relationship in Spring Boot

This article explores data models and security integration solutions for building complex user relationships (such as doctors and patients) in Spring Boot applications. By adopting a hybrid mode of shared user base classes and specific role entities, we can clearly separate common user attributes and role-specific data, effectively manage many-to-many relationships, and achieve flexible permission control based on user roles, while avoiding data redundancy and null values, providing a robust and scalable solution.

Aug 22, 2025 pm 01:45 PM

Java arrays and user input: iteration, boundary management and robustness practices

This article aims to solve the common array out-of-bounds exceptions (IndexOutOfBoundsException) problem when processing user input in Java programs. By analyzing improper loop logic and array indexing operations, we will show how to design a robust iterative process to ensure that data is collected correctly within the limited array capacity and to properly handle user input to avoid program crashes due to index errors or irregular inputs.

Aug 22, 2025 pm 01:39 PM

Visibility management and solutions for external dependencies in Gradle multi-project construction

This article aims to solve the problem that subprojects cannot recognize external dependencies introduced by their dependent modules in Gradle multi-projects. By deeply analyzing the differences between Gradle implementation and API dependency configuration, the article provides two core solutions: one is to adjust the internal dependency configuration of the core module from implementation to API to expose it to consumers, and the other is to directly redeclare the required external dependencies in the consumer module. The article elaborates on the applicable scenarios, advantages and disadvantages of each method, and is supplemented by code examples, aiming to help developers optimize Gradle dependency management and ensure smooth construction of multi-module project.

Aug 22, 2025 pm 01:33 PM

Spring Boot MockMvc Test: How to pass JSON request body object

This article explains in detail how to effectively pass a JSON-format request body object to POST or PUT requests when using MockMvc for REST API testing in Spring Boot applications. For scenarios where the interface expects to receive @RequestBody parameters, the tutorial introduces the complete steps of using Jackson ObjectMapper to serialize Java objects into JSON strings and sending them as request bodies through the contentType and content methods of MockMvcRequestBuilders to ensure that the test can accurately simulate client behavior and verify controller logic.

Aug 22, 2025 pm 01:24 PM

Solutions that cannot be recognized by external dependencies in Gradle multi-project construction

This article discusses the problem that subprojects (such as Interceptor) cannot recognize external dependencies (such as Gson, Rome) introduced by another subproject (such as CommonUtils) in Gradle multi-project construction. The core reason is that Gradle's implementation configuration limits the transitiveness of dependencies. The article provides two main solutions: change the dependency configuration that needs to be exposed in CommonUtils to API, or explicitly redeclare these missing dependencies in the Interceptor project, and deeply analyzes the mechanisms and best practices of Gradle dependency configuration.

Aug 22, 2025 pm 12:51 PM

Android development: Tutorial on enabling buttons after the ProgressBar is loaded

This tutorial details how to automatically enable a button when the ProgressBar loading progress reaches the preset maximum value in Android applications. By configuring the max attribute of ProgressBar and combining mechanisms such as CountDownTimer to simulate or track progress, developers can accurately control the activation timing of buttons, thereby improving the user experience and ensuring the logic of the operation process.

Aug 22, 2025 pm 12:45 PM

How to use a HashMap in Java

The steps to use HashMap are as follows: 1. Import and declare HashMap, such as HashMapmap=newHashMap(); 2. Use put() to add key-value pairs, and repeat keys will overwrite the original value; 3. Use get() to get the value according to the key. When the key does not exist, you can set the default value by getOrDefault(); 4. Use containsKey() to check whether the key exists, and containsValue() to check whether the value exists; 5. Use remove() to delete the entry of the specified key, and specify that the key-value pairs match before deleting it; 6. You can traverse the key through keySet(), entrySet() to traverse the key-value pairs, or use forE

Aug 22, 2025 pm 12:40 PM

java hashmap

Exception handling in Java parallel method calls: Ensure that independent tasks do not interrupt the overall process

This article explores how to handle exceptions thrown by a single task when executing parallel method calls in Java to avoid interrupting the entire parallel processing flow. By adopting a non-instant exception propagation strategy, the exceptions of each task are captured and collected independently, rather than aborting all tasks immediately, ensuring that even if some tasks fail, other tasks can continue to be executed and completed, improving the robustness of the system.

Aug 22, 2025 pm 12:33 PM

Spring Data JPA Projections: Efficient query and mapping specific fields

This article delves into how to efficiently select specific fields from a database and map them to a custom structure in Spring Data JPA. In response to the problem of directly querying some fields with @Query, the article introduces the Spring Data JPA Projections mechanism in detail, including the definition and usage methods of interface projection. Through sample code, it explains how to create a projection interface and use it in Repository to obtain the required data, thereby improving query efficiency and avoiding unnecessary full entity loading.

Aug 22, 2025 pm 12:24 PM

Comparison of minimum values ??in Java arrays: Correct use of OptionalInt vs. alternatives

This article aims to solve the common problem of comparing the minimum values ??of two arrays in Java, especially when using the min() method of the Stream API. We will explore the nature of OptionalInt and its limitations in comparison operations in depth, and provide two effective solutions: one is to safely obtain the original integer value through the getAsInt() method, and the other is to simplify the code using the NumberUtils.min() tool method in the Apache Commons Lang library. The article will contain detailed code examples and notes to help developers write more robust and efficient array minimum comparison logic.

Aug 22, 2025 pm 12:15 PM

Selenium web page loading blank: global retry mechanism implementation

This article describes how to solve the problem of web page loading blank due to unstable network environment or slow server response in Selenium automation testing. By implementing the global retry mechanism, it can automatically refresh and retry when the page loads fail, thereby improving the stability and reliability of the test. We will provide a page load state detection method based on document.readyState and encapsulate it into a reusable function for global application in the Selenium test framework.

Aug 22, 2025 pm 12:03 PM

Solve the 'Multiple Columns of Same Attribute' exception in Vaadin Grid: Understand automatic column generation and manual addition

Vaadin Grid is passed into an entity class (such as new Grid(Audit.class) when initializing, and will automatically create columns for all its properties. If grid.addColumns("propertyName") is then manually called to add the existing property column, it will cause the "Multiple columns for the same property" exception. This article will analyze the root cause of this problem in depth and provide the correct Grid column configuration method to ensure the data is displayed correctly.

Aug 22, 2025 am 11:57 AM

Accessing data members of parent Activity in the startup Activity in Android

This article introduces how to access the data members of the parent Activity in the launched child Activity in Android applications. By migrating business logic to ViewModel, data sharing can be achieved, avoiding direct access to parent Activity objects, thereby improving the maintainability and testability of the code. This article will explain in detail how to use ViewModel and provide sample code.

Aug 22, 2025 am 11:54 AM