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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

java

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

Logback file log configuration in-depth analysis and FAQ troubleshooting

This article discusses in-depth the common reasons and troubleshooting methods for file output not to take effect in the Logback log framework. The core elements of Logback configuration files are analyzed, such as the association mechanism between Appender and Logger, emphasized the importance of root Logger configuration, and provided practical solutions to ensure that logs are correctly written to files, helping developers to effectively solve log output problems.

Aug 08, 2025 am 07:00 AM

Java abstract methods and example methods: Understanding static and non-static context calls

This article aims to explore the calling mechanism of abstract methods and instance methods in Java, especially how to avoid the common error of "non-static methods cannot be referenced from static contexts". We will use a file processing example to analyze abstract classes, concrete implementation classes, and method calls in factory mode in detail, emphasizing the core principle that instance methods must be accessed through object instances.

Aug 08, 2025 am 06:54 AM

How to implement the Comparable interface in Java

To correctly implement the Comparable interface, the first thing to do is to clarify the answer: the compareTo() method must be rewrite to define the natural sorting of objects; 1. compareTo() should return a negative number, zero or positive number to indicate that the current object is less than, equal to or greater than the parameter object; 2. Select a field that determines the natural order (such as id or name); 3. Implement the Comparable interface in the class declaration and rewrite the compareTo() method, and use safe methods such as Integer.compare() to avoid overflow; 4. The object collection can be sorted through Collections.sort() or Arrays.sort(); 5. If sorted by string, use Stri

Aug 08, 2025 am 06:34 AM

java

What is the concept of reflection and its use cases in Java?

Reflection is a powerful feature in Java, allowing programs to dynamically check and operate classes, methods, fields, etc. at runtime. The core answer is: implement dynamic behavior through the java.lang.reflect package and Class class. 1. Frameworks such as Spring, Hibernate, and JUnit use reflection to instantiate objects, inject dependencies, and discover test methods; 2. JSON serialization library (such as Jackson) reads fields and annotations and sets values through reflection; 3. The plug-in system uses Class.forName() to dynamically load classes and creates instances; 4. Runtime annotation processing is judged and executed through isAnnotationPresent; 5. Debugging and testing tools use reverse

Aug 08, 2025 am 06:30 AM

java reflection 概念用例

Writing High-Performance Java Persistence Code with Hibernate

TooptimizeHibernateperformance,firstaddresstheN 1selectsproblembyusingJOINFETCHor@EntityGraphtoloadassociationsinasinglequeryinsteadofmultipleroundtrips.2.Enablebatchfetchingwith@BatchSizeanduseJDBCbatchingwithsession.flush()andsession.clear()everyNo

Aug 08, 2025 am 05:23 AM

java

Java 8 vs. Java 11 vs. Java 17: A Performance Comparison

Java17 has the best performance, followed by Java11, Java8 is the weakest; 1. Java17's ZGC implements millisecond pauses, G1 optimization is significant, better than Java8's ParallelGC; 2. Java17's JIT compiler supports AVX instructions and is more aggressive inline, and CPU-intensive tasks are 5%~15% faster than Java8; 3. Java17's memory management is more efficient, saving 5%~10% memory than Java8 under the same load, and the startup speed is 20%~30% faster with AppCDS; 4. New project recommends Java17, old systems can retain Java8, low-latency scenarios should be selected for Java17 ZGC, and Java11 or Java17 can be used for medium applications; 5. Upgrade construction

Aug 08, 2025 am 05:01 AM

java performance java version

What's New in Java 21: Features and Enhancements

Java21,anLTSrelease,introducesmajorimprovements:1.VirtualThreadsenablehigh-throughputconcurrencywithminimalcodechanges;2.StructuredConcurrency(preview)simplifieserrorhandlingandtaskmanagement;3.PatternMatchingforswitchisstandardized,allowingcleanerda

Aug 08, 2025 am 04:51 AM

new features Java 21