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Analysis of the difference between int to short and long to int type conversion in Java

This article explores the nuances of primitive type conversion in Java, especially the implicit narrowing conversion from int type constant expression to short, and the casting requirements of long type to int. The core lies in the special handling of constant expressions in the Java language specification (JLS 5.2), allowing int-type constants to automatically adapt to smaller integer types within the value range, while long types do not have this convenience. The article will also explain the impact of operator priority on type conversion behavior and explain the context and practicality of this rule design.

Aug 08, 2025 am 08:09 AM

Detailed explanation of the difference between int to short and long to int type conversion in Java

This article explores in-depth the nuances of basic data type conversion in Java, especially the strictness differences between the implicit conversion from int to short and long to int. The core lies in the Java Language Specification (JLS) special assignment conversion rules for constant expressions, which allow int type constant values implicitly narrowed when assigned to byte, short, or char under specific conditions, while long types do not have this special case. The article also explains the priority of type conversion operators and their impact on expression evaluation.

Aug 08, 2025 am 08:06 AM

Understanding and Practice: Correct Calling Strategy for Abstract Methods and Instance Methods in Java

This article explores the calling mechanism of abstract methods and instance methods in Java in depth, focusing on solving the common error of "non-static methods cannot be referenced from static contexts". By analyzing the working principles of abstract classes, concrete subclasses and instance methods, it is clarified that the key to correctly calling such methods is to create instance objects of the class. The tutorial will provide detailed code examples and best practices to help developers master the core principles of method calls in object-oriented programming and ensure the robustness and maintainability of the code.

Aug 08, 2025 am 07:57 AM

How to traverse a matrix without knowing the size

This article introduces how to obtain the number of rows and columns when processing a matrix in Java without knowing the specific size of the matrix and perform effective traversal. The core idea is to understand a matrix as an array of arrays, and use the length attribute of the array to dynamically obtain the dimension information of the matrix, thereby achieving flexible matrix operations.

Aug 08, 2025 am 07:54 AM

What is the key difference between Callable and Runnable in Java?

Callablecanreturnaresultandthrowcheckedexceptions,whileRunnablecannot;1.Runnable’srun()methodhasavoidreturntypeandcannotreturnaresult,whereasCallable’scall()methodreturnsavalueoftypeVretrievedviaFuture;2.Runnablecannotthrowcheckedexceptions,butCallab

Aug 08, 2025 am 07:51 AM

Unable to find a solution for jdk.dio package

This article aims to resolve the issue where the jdk.dio package cannot be found when using OpenJDK 18. By analyzing the source of the jdk.dio package and the difference between Java SE and Java ME, it is clear that the package is not part of Java SE. At the same time, it provides information about the DIO (Device I/O) code base and explains the current situation that the source code of the Java ME version may not be open source, helping developers to understand related background knowledge.

Aug 08, 2025 am 07:51 AM

Solve Java JNI error in VS Code on MacOS Ventura

This article aims to help developers resolve JNI errors encountered when developing Java programs using VS Code on MacOS Ventura systems. This error is usually related to JDK configuration, path issues, or special characters. By checking the JDK version, JAVA_HOME environment variable settings, and project path, you can effectively eliminate and resolve such problems to ensure that the Java program runs smoothly in VS Code.

Aug 08, 2025 am 07:48 AM

Efficient way to extract characters from Java numeric string

This article describes how to efficiently extract characters from Java's numeric strings to avoid redundant code. By using the toCharArray() method or the charAt() method in conjunction with loops, it is easy to process numeric strings of arbitrary lengths, and the corresponding sample code is shown to help developers master simpler and maintainable programming skills.

Aug 08, 2025 am 07:36 AM

Java ArrayList vs. LinkedList: Performance Showdown

Select ArrayList for random access, because the array supports O(1) access, while LinkedList requires O(n) traversal; 2. Select LinkedList when inserting and deleting at the beginning or in the middle and in combination with the iterator, and only the end operation is selected; 3. Select ArrayList for memory-sensitive scenarios, because its memory overhead is much smaller than LinkedList; 4. When the expansion is controllable, ArrayList is more stable, and it is recommended to preset capacity; in summary, most scenarios should be given priority to ArrayList, and only consider LinkedList in specific insertion and deletion modes, and it is necessary to pay attention to the actual performance bottlenecks often look up in location rather than insertion itself.

Aug 08, 2025 am 07:34 AM

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Solve the common problem that Rest Assured dependencies cannot be resolved in Eclipse

This article aims to resolve common problems when io.restassured.RestAssured cannot be parsed when building projects using Maven in the Eclipse IDE. This problem usually stems from a local Maven repository that is damaged or a failed network download. The article will introduce in detail how to ensure that Rest Assured dependencies can be loaded correctly and identified by the project by cleaning local warehouses, updating Maven project configurations, and checking network connections, so as to ensure the stable operation of the development environment.

Aug 08, 2025 am 07:33 AM

Traps of subclass rewriting compareTo method in Java and correct use of Comparator

In Java, when subclasses try to rewrite the compareTo method of the parent class to introduce the subclass's unique comparison logic, they often encounter contract violations. This is because the "natural order" defined by the Comparable interface requires that comparison operations must meet strict contracts such as transitiveness and symmetry. A subclass directly rewrites compareTo and changes its parameter type or behavior will lead to logical contradictions when compared with the parent class instance, destroying the correctness of the collection class (such as TreeSet). The solution is to avoid changing the natural order through Comparable in the inheritance chain, but instead use an external Comparator interface to define custom sorting logic for a specific type or complex inheritance relationship.

Aug 08, 2025 am 07:30 AM

Alternatives to use the jdk.dio.mmio package in Java SE

This article aims to answer the problem that the jdk.dio.mmio package cannot be found in Java SE environments such as OpenJDK 18. This package is part of Java ME (Micro Edition), not part of Java SE. The article will explain the reasons and provide alternatives and related resources to implement similar device I/O capabilities in a Java SE environment to help developers understand and solve such problems.

Aug 08, 2025 am 07:21 AM

Design of OTP security verification system based on time limit and uniqueness

This article aims to explore and resolve possible security vulnerabilities in OTP (one-time password) verification systems, especially the OTP collision problems that may arise when multiple users register within a similar time. The article will propose an OTP system design scheme combining time limit and uniqueness verification to improve the security of the system and reduce security risks caused by accidental factors.

Aug 08, 2025 am 07:18 AM

Challenges and strategies for converting Object safe to generic HashMap in Java

In Java, it is a common challenge to convert an Object type safely to a HashMap with specific generic parameters. Due to Java's type erasing mechanism, generic type parameters cannot be checked directly at runtime, resulting in simple type conversions that may raise unchecked warnings or runtime errors. This article will explore the root causes of this problem, analyze common mistake attempts, and propose more robust design patterns and practice methods to avoid unsafe downward transformation of Objects, thereby improving the type safety and maintainability of the code.

Aug 08, 2025 am 07:09 AM