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Technical Articles

Java

A deep understanding of Java object memory allocation: the impact of methods and interfaces

This article discusses the memory allocation mechanism of objects and methods in Java in depth. The core point is that Java methods are loaded only once when the class is loaded and stored in the method area, rather than each object instance has an independent memory copy of its method. The memory allocated by an object on the heap is mainly used to store its instance fields and a small amount of object header information. Therefore, even if a subclass object is referenced through an interface type, the subclass-specific method does not allocate additional memory for that particular object, because the method itself is a class-level resource.

Aug 12, 2025 am 10:48 AM

How do you implement a singleton pattern in Java?

ThesingletonpatterninJavaensuresaclasshasonlyoneinstanceandprovidesglobalaccess,withimplementationchoicesdependingonrequirements:eagerinitializationcreatestheinstanceatclassloading,ensuringthreadsafetybutlackinglaziness;lazyinitializationwithdouble-c

Aug 12, 2025 am 10:41 AM

How to convert a string to an integer in Java?

The most common method to convert a string to an integer is to use Integer.parseInt(). 1. Use Integer.parseInt() to convert the string to a basic type int, but the string must be a valid number, otherwise a NumberFormatException will be thrown; 2. To avoid exceptions, try-catch should be used to handle invalid input or null values; 3. You can remove whitespace characters through trim() to ensure the conversion is successful; 4. For different hexadecimal or binary, you can use Integer.parseInt(str,radix) or Integer.decode(); 5. If you need to return Inte

Aug 12, 2025 am 10:35 AM

Flexible matching of keys in Java Properties files: Handle partial key name search issues

This article explores the solution when you need to find the corresponding value based on part of the key name (rather than the full key name) in the Java java.util.Properties file. Since the getProperty() method only supports exact matching, the article introduces how to flexibly locate and obtain the required values by iterating over all key collections of Properties objects and combining string matching methods such as contains() or endsWith() to meet the needs of dynamic or partial key name searches.

Aug 12, 2025 am 10:12 AM

What are arrays in Java?

ArraysinJavaarefixed-size,type-safedatastructuresthatstoremultiplevaluesofthesametypeincontiguousmemorylocations,withindexingstartingat0;theyaredeclaredusingsyntaxlikeint[]numbers=newint[5]orinitializedwithvaluessuchasint[]scores={85,90,78,95,88},all

Aug 12, 2025 am 10:03 AM

java array

How to compare Strings in Java

Use .equals() to compare string content, because == only compare object references rather than actual characters; 2. Use .equalsIgnoreCase() when comparing ignoring case; 3. Use .compareTo() when sorting alphabetically, and .compareToIgnoreCase() when ignoring case; 4. Avoid calling strings that may be null. Equals() should be used to use "literal".equals(variable) or Objects.equals(str1,str2) to safely handle null values; in short, always pay attention to content comparison rather than reference,

Aug 12, 2025 am 10:00 AM

java String comparison

Solve the problem that the database is not selected after the JDBC connection MySQL is automatically reconnected

This article discusses the root cause of the "No database selected" error when JDBC connects to MySQL because the autoReconnect property and the connection URL do not specify the database name, resulting in a long-term operation. The working principle of the automatic reconnect mechanism is analyzed in detail, and two solutions are provided: it is recommended to always include the database name in the connection URL, and to utilize the createDatabaseIfNotExist property if needed. It aims to help developers build more stable and reliable database connections.

Aug 12, 2025 am 09:57 AM

Deep understanding of the compilation types in jstat -printcompilation output

This article explores the output of the jstat -printcompilation command, especially the meaning of the Type column. This column indicates the type of JIT compilation, including regular compilation, on-stack replacement, and local method compilation. However, it should be noted that in standard JDK releases, the Type column is usually only displayed as 1 (regular compilation) due to the limitations of specific debug options, and other types are only visible in specially configured debug JVMs. Understanding this is essential for an accurate interpretation of JIT compilation activities.

Aug 12, 2025 am 09:39 AM

How to split a String in Java

Usesplit(regex)todivideastringintosubstringsbasedonadelimiter,returningaString[]array.2.Forwhitespace,use"\s "tohandlespaces,tabs,orlinebreakseffectively.3.Escapespecialregexcharacterslike.or|usingdoublebackslashes(e.g.,"\."or&quo

Aug 12, 2025 am 09:38 AM

java String splitting

Find the parent node of a specified node in a general tree: an implementation based on breadth-first search

This article details how to find the parent node of a specified node in a general tree data structure. We will adopt a Broadness-first search (BFS) strategy to check whether the child nodes of each node are the target nodes by traversing each layer of the tree. The tutorial will provide Java sample code to demonstrate how to use queues to implement this process, and discuss related precautions to help readers master the traversal and search techniques of general tree.

Aug 12, 2025 am 09:30 AM

Java JAR application output management: console display and log redirection policy

The output of System.out.println is usually invisible when a Java application is packaged into a JAR file and run with a double-click. This article will explore the reasons for this phenomenon in depth and provide two core solutions: one is to realize background logging by redirecting standard output streams and error streams to files; the other is to execute JAR files through command lines or scripts to ensure real-time visibility of console output. Mastering these methods can effectively manage the debugging information and running status of JAR applications.

Aug 12, 2025 am 09:15 AM

What is the final keyword in Java?

ThefinalkeywordinJavapreventschangestovariables,methods,orclasses.Afinalvariablecannotbereassignedafterinitialization,thoughthestateofamutableobjectitreferencescanstillbemodified.Afinalmethodcannotbeoverriddeninasubclass,ensuringconsistentbehavior.Af

Aug 12, 2025 am 08:59 AM

java final

Data loss in Java methods: Understanding parameter passing and data persistence

This article explores the common problems of data loss after Java method calls, especially when the method reassigns incoming reference type parameters. We will explain Java's parameter passing mechanism and provide two effective solutions: passing data through method return value, and directly modifying the content of the incoming reference type object. Help developers avoid such problems through specific code examples and precautions, ensuring that data is correctly passed and persisted between methods.

Aug 12, 2025 am 08:33 AM

Guide to Socket Exception Handling and Data Flow Selection in Java Network Programming

This article discusses the common Socket exceptions in Java network programming, especially the connection reset and stream corruption that may be encountered when using ObjectInputStream/OutputStream. The article analyzes the limitations of ObjectStream in network communication, emphasizes the importance of preset "exception path", and proposes more robust data exchange solutions such as BufferedReader/BufferedWriter, JSON, XML or Protobuf, aiming to help developers build stable and reliable network applications.

Aug 12, 2025 am 08:30 AM