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JSON object data extraction in Java: Avoid common pitfalls

This tutorial explains in detail how to extract specific data from JSON strings using JSON libraries such as org.json in Java. By directly parsing the JSON string into a JSONObject and using its key names for data retrieval, it can effectively avoid common parsing errors such as NullPointerException, and ensure the accuracy and efficiency of data extraction.

Aug 24, 2025 am 11:18 AM

Java merge sorting: Fix array element coverage problem and code optimization

This article aims to solve the problem of array element overwriting that occurs when Java implements merge sorting, which causes sorting to only handle a small number of elements. The article will analyze the problem code, point out the cause of the error, and provide a modified code example. In addition, code style optimization will be discussed, and it is recommended to use interfaces instead of specific classes for programming.

Aug 24, 2025 am 11:06 AM

Solve the problem of Predicate type mismatch in Java Stream

This article aims to resolve compilation errors caused by the Predicate type mismatch when using anyMatch method in Java Stream. Help developers write more robust and maintainable code by analyzing the causes of problems and providing a variety of solutions, including using maps for type conversion, leveraging Java 16's mapMulti features, and improving method design.

Aug 24, 2025 am 10:57 AM

Use Stream.collect() to correctly collect EnumSet

This article describes how to correctly provide Supplier when collecting EnumSet using the Java Stream API's collect() method. The focus is on explaining the usage of the three parameter versions in the Stream.collect() method, and how to simplify the code using the Collectors.toCollection() method to avoid type mismatch errors.

Aug 24, 2025 am 10:51 AM

How to group by in Java Streams?

GroupingBy() can easily implement grouping of elements in Java streams, and its function is similar to SQL's GROUPBY; the elements are organized into maps through classification functions, the keys are grouped values, and the values ??are element lists; counting() can be used to counting() to count the number of each group, and using mapping() to convert elements, supporting nested grouping and custom map or collection types, so as to handle data grouping requirements flexibly and efficiently.

Aug 24, 2025 am 10:40 AM

Troubleshooting and solutions for getting JSP Session attributes as NULL

This article aims to solve the problem of using session.getAttribute() in JSP to get attribute value NULL. We will dig into the scope concept in JSP, analyze the causes of this problem, and provide effective ways to share data between different browser windows using application scopes, while providing sample code and considerations to help developers better understand and solve similar problems.

Aug 24, 2025 am 10:39 AM

Deeply understand the memory management and optimization strategies of Spring singleton beans

Spring singleton beans are a single instance of the application context, and their life cycle is synchronized with the application context. Although stateless singleton beans have little impact on memory usage, stateful singleton beans may become the main cause of memory consumption if they hold a large amount of data. This article aims to explore how to effectively manage the memory of a stateful singleton bean. By introducing a cache mechanism and setting expired policies, such as using Spring's cache abstraction or directly integrating memory cache libraries such as Caffeine and Guava, it can realize on-demand loading and timely release of internal data, thereby optimizing memory usage, avoiding unnecessary memory residency, and maintaining the characteristics of a singleton bean.

Aug 24, 2025 am 10:33 AM

Android custom Dialog cannot dismiss the solution

This article aims to solve the problem that custom Dialog cannot dismiss properly in Android development. By analyzing common reasons, an effective way to manage Dialog instances as class member variables and display and close when needed. At the same time, it is recommended to place Dialog initialization and style settings inside the Dialog class to improve the maintainability and readability of the code.

Aug 24, 2025 am 10:27 AM

Efficient way to build BigInteger from byte arrays

This article aims to describe how to efficiently convert an array of bytes into a BigInteger object, especially when handling encrypted or encoded data, such as encoded one byte into four bytes. We will explore ways to avoid unnecessary binary conversions and loops, directly use byte arrays to build BigInteger, and provide sample code and precautions for flexible use in practical applications.

Aug 24, 2025 am 10:15 AM

Use Java Stream to find Map with maximum value in List

This article describes how to use the Java Stream API to find a HashMap with the largest Length value from an ArrayList. The article first suggests using custom objects instead of HashMap to improve code readability and type safety. Then, we explain in detail how to find a single largest element using Stream.max() and Collections.max(), and how to find all the collections of elements with maximum values ??using groupingBy() and collect(), and provide the corresponding sample code.

Aug 24, 2025 am 10:12 AM

Retrieve data of JSON objects from JSON Simple library

This article describes how to retrieve data from JSON objects using the JSON Simple library. With a simple example, it demonstrates how to parse a JSON string containing a username, address, and password and use the get() method to get the value of a specific key. This article will help you understand the basic usage of the JSON Simple library and avoid common null pointer exceptions.

Aug 24, 2025 am 10:09 AM

Automatically inject dependencies and Mock objects with JMockit

This article describes how to use the JMockit framework to automatically inject dependencies and Mock objects into test classes. With @Tested and @Injectable annotations, instances of the tested class can be easily created and their dependencies are automatically injected into the Mock object, thus simplifying the writing process of unit testing. The article also provides a simple example that demonstrates how to use JMockit for dependency injection and Mock object creation, and emphasizes the importance of configuring JMockit Java Agent.

Aug 24, 2025 am 10:03 AM

Mocking WebClient requests with Mockito: Solve FAQs in unit testing

This article aims to address how to use Mockito in unit tests to get the expected response when sending requests using WebClient. The article will analyze common errors and provide feasible solutions, including how to properly mock the WebClient object and how to handle parameter matching issues for the BodyInserters.fromValue() method.

Aug 24, 2025 am 10:00 AM

Tutorial: How to exit loop through user input in Java

This tutorial is designed to explain how to flexibly exit a for loop or while loop through user input in a Java program. We will introduce how to use the BufferedReader class to read user input and determine whether the input is an exit instruction in the loop, thereby achieving flexible control of the program. At the same time, some code optimization suggestions will be provided to help you write more concise and efficient Java code.

Aug 24, 2025 am 09:48 AM