Java Concurrency Patterns for Complex Problems
Thread-SafeSingleton uses the Initialization-on-DemandHolder mode to ensure thread safety and avoid explicit synchronization; 2. Producer-Consumer mode uses BlockingQueue to decouple producers and consumers, and uses its blocking characteristics to achieve efficient and thread-safe task delivery, suitable for event processing and logging systems; 3. WorkerThreadPool manages thread resources through ThreadPoolExecutor, sets core and maximum number of threads, bounded queues and reasonable rejection strategies, improves task scheduling efficiency and prevents resource exhaustion, widely
Aug 06, 2025 pm 12:29 PM
Java Performance Tuning: A Guide to JVM Optimization
First of all, we must clarify the answer: the core of JVM tuning is to reasonably configure memory, choose appropriate GC policies and continuously monitor. 1. Understand the JVM memory structure and focus on optimizing the ratio of the new generation to the elderly in the heap; 2. Select the GC type according to the application scenario, and recommend G1 or ZGC to balance the delay and throughput; 3. Finely set the -Xms, -Xmx, -Xmn and Metaspace parameters to avoid dynamic capacity expansion overhead; 4. Turn on the GC log and use GCViewer or GCEasy analysis to adjust the strategy based on the data; 5. Avoid code traps such as large object creation, memory leaks, and frequent string splicing; 6. Continuous monitoring of tools such as jstat, jmap, jstack and Prometheus to build
Aug 06, 2025 pm 12:13 PM
how to get size of arraylist in java
Getting the size of an ArrayList in Java should use the size() method. This method returns the number of elements actually stored in the current ArrayList, rather than the capacity of the internal array, and its time complexity is O(1), which is very efficient. 1. Using size() is the most direct and recommended way; 2. The empty ArrayList call size() just created will return 0; 3. Size() is different from capacity. The former represents the actual number of elements, while the latter is the maximum number that the internal array can accommodate; 4. It is not recommended to obtain the size by traversing manual counting, which is inefficient and redundant. So, getting the size of ArrayList just call intsize=arrayLis
Aug 06, 2025 am 11:45 AM
Solving Common Memory Leaks in Java Applications
Staticfieldsholdingobjectreferencescanpreventgarbagecollection;useWeakHashMaporcleanupmechanisms.2.Unclosedresourceslikestreamsorconnectionscauseleaks;alwaysusetry-with-resources.3.Non-staticinnerclassesretainouterclassreferences;makethemstaticoravoi
Aug 06, 2025 am 09:47 AM
What is the Observer design pattern and how can it be implemented in Java?
TheObserverdesignpatternenablesautomaticnotificationofstatechangesfromasubjecttomultipleobservers,ensuringconsistencywithouttightcoupling.1.Thesubjectmaintainsalistofobserversandnotifiesthemwhenitsstatechanges.2.Observersregisterwiththesubjectandimpl
Aug 06, 2025 am 09:41 AM
The Evolution of Java: From JDK 8 to JDK 21
JavaevolvedsignificantlyfromJDK8toJDK21,with1.JDK8introducinglambdas,streams,Optional,andthenewDate/TimeAPI;2.JDK9–17addingtheModuleSystem,var,switchexpressions,records,andsealedclasses;3.JDK21deliveringvirtualthreads,patternmatchingforswitch,sequenc
Aug 06, 2025 am 09:04 AM
How to capture chart screenshots in MPAAndroidChart and share with Intent
This article details how to efficiently capture screenshots of BarChart (or other charts) in Android applications without permanently saving the image to device storage, and share it to other social media or apps through Android's Intent mechanism. The tutorial covers the complete steps and sample code for getting a chart bitmap, generating temporary URIs, and building a sharing Intent.
Aug 06, 2025 am 09:00 AM
Delete temporary images when converting Docx4j documents to PDF
This document is intended to solve the problem that when converting Word documents to PDF using Docx4j, images in the header and footer are saved in the default /tmp directory, resulting in the inability to effectively clean up temporary files. The article will elaborate on the root cause of the problem and provide a temporary solution to avoid using images in the header and footer, while pointing out that the problem has been submitted to Docx4j official as a bug.
Aug 06, 2025 am 08:51 AM
Building RESTful APIs in Java with JAX-RS
JAX-RS is a standardized method for building RESTful APIs in Java, simplifying REST service development through annotations. 1. JAX-RS is a specification of JakartaEE and needs to rely on Jersey, RESTEasy or ApacheCXF, etc. to implement; 2. Use @Path, @GET, @POST and other annotations to map Java methods to HTTP endpoints; 3. Define the data format through @Produces and @Consumes, and combine it with Jackson and other libraries to achieve JSON serialization; 4. You can register resource classes through ResourceConfig and start the service using an embedded server (such as Grizzly); 5. Recommended use
Aug 06, 2025 am 08:49 AM
Guide to convert single/double digit month strings to LocalDate format in Java
This article details how to efficiently and safely convert single or double-digit strings (representing months) into LocalDate objects in Java, and specify year and day. We will explore using LocalDate.of() to create a new date and using the withMonth() method to modify the month of an existing date. At the same time, the article emphasizes key input checksum exception handling to ensure the robustness and accuracy of data transformation.
Aug 06, 2025 am 08:48 AM
Java LocalDate: A practical guide to converting single/double digit strings to date formats
This article explains in detail how to convert a single/double digit string representing a month (such as "2" or "10") in Java to a LocalDate object with a fixed year and date. The tutorial covers the ways to create new dates with LocalDate.of() and modify existing dates with withMonth(), while highlighting the importance of rigorous verification and error handling of inputs during the transformation process to ensure data consistency and application robustness.
Aug 06, 2025 am 08:39 AM
Java Memory Leaks: How to Find and Fix Them
Discover memory leaks, you need to observe the continuous growth of memory, frequent FullGC invalidation, and OOM exceptions, and use jstat or monitoring tools to analyze the trend; 2. Generate HeapDump file (automatically triggered by jmap command or -XX: HeapDumpOnOutOfMemoryError); 3. Use EclipseMAT and other tools to analyze the .dump file to check the number of abnormal objects, reference chains and common leak points such as static collections, ThreadLocal, and unclosed resources; 4. When repairing, use weak references, try-with-resources, timely removeThreadLocal, log off the listener, and static internal classes to replace non-static; 5. Prevent it from IDE
Aug 06, 2025 am 08:28 AM
Processing of variable-length byte arrays in RSA encryption: Solve the problem of decrypted data misalignment
When RSA encrypts a byte stream (such as image data), directly using BigInteger.toByteArray() will convert the encrypted BigInteger into a variable-length byte array. When these variable-length arrays are simply spliced and written to a file, the decryption end cannot accurately identify the boundaries of each encryption block, resulting in data misalignment and decryption failure. The core solution is to append its length information before each encryption block, ensuring that the original BigInteger can be read correctly and reconstructed during decryption.
Aug 06, 2025 am 08:21 AM
Polymorphism processing of abstract class fields in Java: JSON deserialization and runtime type judgment
This article aims to explore the challenges of dealing with abstract class field polymorphism in Java classes, especially how to correctly identify and instantiate concrete subclasses when deserializing from JSON data. The article will explain in depth how to use the Jackson library's @JsonTypeInfo and @JsonSubTypes annotations to achieve polymorphic deserialization, as well as how to safely access subclass-specific properties through instanceof operators and casts at runtime, thus building a flexible and robust system.
Aug 06, 2025 am 08:15 AM
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