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Technical Articles

Java

javaTutorial

How to use Optional in Java?

UseOptional.empty(),Optional.of(),andOptional.ofNullable()tocreateOptionalinstancesdependingonwhetherthevalueisabsent,non-null,orpossiblynull.2.CheckforvaluessafelyusingisPresent()orpreferablyifPresent()toavoiddirectnullchecks.3.Providedefaultswithor

Aug 22, 2025 am 10:27 AM

java optional

How to map elements in a Java Stream

Mapping elements in JavaStream uses the map() method, which converts each element into another object through the provided function. 1. Use map() to convert elements, such as converting strings to uppercase or extracting object fields; 2. Use flatMap() to process nested structures to flatten the generated stream into a single-layer stream; 3. Multiple mapping operations can be called chain-based and filtered to process complex conversions. Map() or flatMap() should be selected based on the input element to generate a single or multiple values, and the mapping does not modify the original data. Collect() is required to obtain the final collection. Mapping is the core method of processing data in JavaStreamsAPI in functional programming.

Aug 22, 2025 am 10:21 AM

Spring Boot app cannot get configuration solutions from Configuration Center

This article aims to resolve an issue where Spring Boot applications cannot get configuration from Spring Cloud Config Server. We will explore possible reasons and provide detailed configuration steps and precautions to ensure that your application can be properly connected to the configuration center and load configuration information dynamically, thereby enabling centralized management of configurations and dynamic updates.

Aug 22, 2025 am 10:21 AM

String inversion and character increment: Detailed explanation of Java implementation

This article will introduce in detail how to implement string inversion using Java and increment each character in the string. We will provide complete code examples, including functions that invert strings and increment characters, and discuss some boundary situations that need attention, helping you understand and master common techniques for string processing.

Aug 22, 2025 am 10:12 AM

How to use the Pattern and Matcher classes in Java?

The Pattern class is used to compile regular expressions, and the Matcher class is used to perform matching operations on strings. The combination of the two can realize text search, matching and replacement; first create a pattern object through Pattern.compile(), and then call its matcher() method to generate a Matcher instance. Then use matches() to judge the full string matching, find() to find subsequences, replaceAll() or replaceFirst() for replacement. If the regular contains a capture group, the nth group content can be obtained through group(n). In actual applications, you should avoid repeated compilation patterns, pay attention to special character escapes, and use the matching pattern flag as needed, and ultimately achieve efficient

Aug 22, 2025 am 09:57 AM

java regular expression

Deeply understand the memory usage and efficient management strategies of Spring singleton beans

Singleton beans in the Spring framework are created and reside in the application context when the application is started until the application is closed. For stateless singleton beans, the memory overhead is usually minimal. However, if the bean is holding a large amount of dynamic state data internally, it can lead to a significant memory footprint. For this kind of situation, it is recommended to use a cache mechanism with expired policies (such as Spring cache abstraction or Caffeine/Guava, etc.) to manage the data life cycle, thereby effectively releasing memory resources that are no longer used.

Aug 22, 2025 am 09:57 AM

Restriction and circular dependency solutions for this reference in Java constructor

In Java, this cannot be referenced before the inheritance class constructor calls super() internally, which often leads to a compilation error of "Cannot reference 'this' before supertype constructor has been called". This problem stems from the order of initialization of Java objects: the parent class constructor must be completed before the subclass instance can be considered fully initialized. The problem is particularly prominent when there are circular dependencies between objects and these dependencies are established in the constructor through the final field. This article will explore this limitation in depth and provide professional references to address such problems through strategies such as removing circular dependencies, relaxing field invariance, or reconstructing design.

Aug 22, 2025 am 09:54 AM

what is an enum in java

AnenuminJavaisaspecialdatatypefordefiningafixedsetofconstants,usedwhenavariableshouldonlyholdvaluesfromapredefinedlist.1.Enumsaredefinedusingtheenumkeyword,suchaspublicenumDay{MONDAY,TUESDAY,...,SUNDAY}.2.Theyprovidetypesafety,ensuringonlydeclaredcon

Aug 22, 2025 am 09:49 AM

What is a Map in Java?

AMapinJavaisaninterfacethatstoresdataaskey-valuepairs,allowingretrievalofvaluesbytheirkeys;itisnotpartoftheCollectioninterfacebutisacorecomponentoftheJavaCollectionsFramework;eachelementisakey-valuepair(Map.Entry),keysareunique,eachkeymapstoonlyoneva

Aug 22, 2025 am 09:16 AM

Debug your 'Teen Talk' program: Solve infinite loop problems

This article aims to help you debug a Java program called "Teen Talk" that is designed to simulate how teenagers talk, adding "like" after each space. By analyzing the infinite loop problem in the code and providing modified code examples, this article will guide you to solve the problem that the program cannot run and provide more efficient implementation ideas.

Aug 22, 2025 am 09:12 AM

Complete tutorial for converting Android views into images and sharing

This tutorial is designed to guide developers how to convert any view into images in Android apps and share it to platforms such as WhatsApp, Skype, and Mail. The article will provide a detailed description of how to use DrawingCache technology to capture view content and save it as a picture file. At the same time, sample code for sharing pictures to other applications will be provided, and compatibility suggestions are provided for Android 6 to Android 10 devices to ensure that the applications can run normally on these devices.

Aug 22, 2025 am 08:57 AM

The strategy of comparing the minimum value of an array with the processing of OptionalInt in Java

This article aims to explore common problems and solutions for comparing the minimum values ??of two arrays in Java. When using the Arrays.stream().min() method, its return type is OptionalInt, resulting in the inability to directly perform numerical comparisons. The article will introduce in detail how to get the original int value by calling the getAsInt() method of OptionalInt, and how to use the NumberUtils.min() method in the Apache Commons Lang library to achieve a more concise and robust minimum value comparison.

Aug 22, 2025 am 08:48 AM

How to find data through partial key values ??in Java Properties file

This tutorial aims to solve the problem of how to retrieve the corresponding value when only part of the key is known in Java Properties files. By traversing all keys using the stringPropertyNames() method of the Properties class and combining string matching technology (such as contains()), flexible data search based on partial keys can be effectively implemented, suitable for scenarios where key structure is complex or requires fuzzy matching.

Aug 22, 2025 am 08:45 AM

Extract LinearSVC model coefficients and intercepts from Apache Flink ML

This article describes how to extract hyperplanar parameters, including coefficients and intercepts, from Apache Flink ML-trained LinearSVC model. By extracting these parameters, users can integrate model rules into Flink CEP's pattern matching API to implement more complex stream processing logic. This article provides Python and Java sample code to help users get started quickly.

Aug 22, 2025 am 08:33 AM