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Java tutorial on extracting substrings between the beginning and end vowels in strings

This article aims to guide developers how to extract substrings from the first vowel to the last vowel in a string using Java. This function can be achieved concisely and efficiently by using regular expressions. This article will provide detailed code examples and explanations to help readers understand and master the method and avoid common StringIndexOutOfBoundsException errors.

Aug 08, 2025 am 08:39 AM

Security discussion and best practices based on one-time password (OTP) verification

This article discusses in depth the security risks that may exist in verification systems based on one-time passwords (OTP), especially when the OTP generated by user A is accidentally guessed and successfully verified. The article analyzes the probability of this risk and proposes to enhance the security of the OTP system by limiting the validity period of OTP, preventing reuse, and adopting safer generation algorithms, thereby effectively reducing the risk of being brute-forced or accidentally guessed.

Aug 08, 2025 am 08:36 AM

Exactly validate the 'true' and 'false' values using Java regular expressions

This article describes how to use Java to accurately verify whether a string is "true" or "false". Simple string comparison avoids the possible misjudgment of regular expressions and provides a concise and efficient solution to ensure that only the two strings "true" or "false" can pass the verification.

Aug 08, 2025 am 08:30 AM

Subtle differences in type conversion in Java: from int to short vs. from long to int

This article deeply explores the special rules of basic data type conversion in Java, especially the behavioral differences between int to short and long to int. The core lies in the provisions on "assignment conversion" in the Java Language Specification (JLS), especially for the special treatment of constant expressions. We will use specific code examples to analyze why some seemingly similar type conversion operations can lead to compilation errors, while others can pass smoothly, and explain the considerations behind this design to help developers better understand Java's type system.

Aug 08, 2025 am 08:27 AM

Check whether the sorted subarray of size k is included in the sorted array of size n, with complexity O(log n)

This tutorial introduces an efficient way to find sorted subarrays in a sorted large array. The core idea is to use binary search to locate the starting element of the subarray, and then verify whether the subsequent elements of the subarray exist continuously in the large array. This method is completed within the time complexity of O(max(log n, k)), where n is the size of a large array and k is the size of a subarray. When n is much larger than k, the time complexity is close to O(log n).

Aug 08, 2025 am 08:21 AM

Security analysis and design suggestions based on one-time password (OTP) verification

This article explores potential security vulnerabilities in mailbox verification systems based on one-time passwords (OTP), that is, when users register but do not verify, other users may use the same OTP to complete verification through accidental guessing or brute force. The article analyzes the possibility of this attack and proposes how to design a more secure OTP system, including limiting the validity period of OTP, preventing OTP reuse, and using deterministic encryption algorithms to generate OTP.

Aug 08, 2025 am 08:18 AM

How do autoboxing and unboxing work in Java?

Autoboxingconvertsprimitivestowrapperobjectsandunboxingconvertswrapperobjectstoprimitives,enablingseamlessinteractionbetweenthem.1.Autoboxingoccurswhenassigningaprimitivetoawrappervariable,suchasIntegernum=100,wherethecompilercallsInteger.valueOf(100

Aug 08, 2025 am 08:09 AM

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