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How to work with dates and times in Java 8 (java.time)?

It is recommended to use the java.time package to handle dates and times in Java 8 and above. 1. LocalDate and LocalTime are used for dates and times without time zones, such as 2025-04-05 and 14:30:45 respectively; 2. Use now() to get the current date or time, and of() to create a specified date or time; 3. Common operations include adding and subtracting days, months, etc., and the object is immutable, and each operation returns a new instance; 4. LocalDateTime combines date and time but no time zone, ZonedDateTime supports time zone; 5. Use ZoneId to define the time zone and convert it through atZone(), and use withZoneSameInstan

Jul 07, 2025 am 02:15 AM

date time Java 8+

Understanding Java ClassLoader Hierarchy and Delegation Model

The JavaClassLoader hierarchy consists of a parent-child structure consisting of Bootstrap, Extension and ApplicationClassLoader. The delegate priority model is adopted to ensure the consistency and security of core classes. Class loading problems are common in classpath errors or class loader isolation. When troubleshooting, you need to check dependencies, logs and use -verbose:class parameters; custom ClassLoader needs to inherit and rewrite findClass() to avoid duplicate loading and pay attention to the hot replacement mechanism.

Jul 07, 2025 am 02:09 AM

java

Persistent Data Storage using Java JPA and Hibernate

JPA is a Java persistence specification, and Hibernate is its commonly used implementation. 1. JPA defines object and database mapping standards, and Hibernate is responsible for specific operations. 2. Entity classes map table structures through @Entity, @Table, @Id, @GeneratedValue, etc. 3. The association relationship is processed through annotations such as @OneToMany, @ManyToOne, etc., and pay attention to mappedBy and cascading configuration. 4. In SpringBoot, you can quickly complete persistence operations by configuring data sources and using SpringDataJPA.

Jul 07, 2025 am 02:05 AM

java

Exploring Modern Java 8 Language Features

Java 8 and subsequent versions have introduced a number of key features, significantly improving the simplicity, security and maintainability of the code. 1. Lambda expressions allow functions to be passed as parameters, simplifying the redundant writing of anonymous internal classes, and are suitable for the implementation of functional interfaces; 2. StreamAPI supports declarative processing of collection data, and improves data processing capabilities through operation chains such as filters and maps, but attention should be paid to performance and simple logic scenarios; 3. The Optional class reduces null pointer exceptions by explicitly processing possible missing values, and is recommended for return types rather than construction or setting methods; 4. The interface defaults and static methods enhance the expansion capabilities of the interface to avoid destroying existing implementations, and is suitable for adding compatibility methods or tool methods; 5.

Jul 07, 2025 am 02:00 AM

What are bounded wildcards?

Bounded wildcards in Java generics are implemented through the ? symbol, allowing upper and lower limits to type parameters. 1. The upper limit wildcard character (?extendsT) limits the type to T or its subclass. It is suitable for scenarios where data is read from structures, but elements are not allowed to be added. 2. The lower limit wildcard character (?superT) limits the type T or its parent class. It is suitable for scenarios where data is written to the collection. Elements of type T can be added. 3. Unbounded wildcards (?) represent completely unknown types and are suitable for methods that operate across all types. Elements can only be treated as Objects. When using it, you should select the appropriate wildcard according to the read and write needs to improve code flexibility and security.

Jul 07, 2025 am 01:57 AM

Using Java BlockingQueue Implementations for Concurrency

BlockingQueue is an important tool for thread collaboration in Java concurrent programming. It provides a thread-safe queue structure and automatically blocks fetch/drop operations when the queue is empty or full, which is very suitable for the producer-consumer model. 1. Common implementation classes include ArrayBlockingQueue (bounded array queue), LinkedBlockingQueue (optional bounded link queue), SynchronousQueue (synchronous queue that does not store elements), PriorityBlockingQueue (unbounded queue that supports priority sorting) and DelayQueue (queue that can only be retrieved after the delay expires). 2. In the producer-consumer model

Jul 07, 2025 am 01:53 AM

java

Performance Tuning and Profiling Java Applications

The key steps for Java application performance tuning include: 1. Use JVM built-in tools such as jstat, jmap, and jstack to monitor GC frequency, memory distribution and thread status, and locate basic problems; 2. Use VisualVM, JProfiler or AsyncProfiler to analyze hot codes and identify CPU-intensive methods; 3. Optimize garbage collection behavior through GC logs and parameter adjustments, and select appropriate recyclers and heap configurations based on business load testing; 4. Avoid common traps such as excessive synchronization, frequent object creation, N 1 query, and excessive log output, and reduce unnecessary performance losses.

Jul 07, 2025 am 01:52 AM

java Performance tuning

How to implement thread synchronization in Java?

Common methods for handling thread synchronization in Java include: 1. Use synchronized keywords, which can be used for methods or code blocks, ensuring that only one thread executes key code at the same time; 2. Use ReentrantLock to provide a more flexible lock mechanism, supporting attempts to acquire locks, timeouts and fair strategies; 3. Use advanced tools in the java.util.concurrent package such as Semaphore to control resource access; 4. Avoid excessive synchronization, lock only necessary parts and pay attention to avoid deadlocks. These methods help developers effectively manage shared resources and ensure thread safety.

Jul 07, 2025 am 01:45 AM

Best Practices for Java Synchronization Mechanisms

To control the granularity with synchronized, you should give priority to the use of synchronized code blocks; you should give priority to tool classes such as ReentrantLock and ConcurrentHashMap in the java.util.concurrent package; you should unify the lock order and use tryLock; volatile can ensure variable visibility but does not replace synchronization. Specifically: 1. When using synchronized, you should prioritize synchronizing code blocks rather than the entire method to lock resources that really need to be protected; 2. Use ReentrantLock to provide a more flexible locking mechanism, ReadWriteLock improves the performance of read more and write less scenes, and ConcurrentHas

Jul 07, 2025 am 01:37 AM

mechanism Java Sync

Implementing Java Serialization and Deserialization

Java serialization is the process of converting an object into a byte stream for storage or transmission, while deserialization is the process of restoring an object. 1. Implement the Serializable interface to enable serialization function; 2. Use ObjectOutputStream to write objects to files or networks; 3. Use transient keyword to exclude sensitive fields; 4. Define serialVersionUID to improve class version compatibility; 5. Deserialization requires ObjectInputStream and ensure that the class path exists; 6. Nested objects also need to implement Serializable; 7. Avoid deserializing untrusted data to prevent security risks. Note that native serialization performance is low, it is recommended to use J in large-scale scenarios.

Jul 07, 2025 am 01:32 AM

java Serialization

Understanding Java Garbage Collection Processes

Java garbage collection (GC) is a mechanism by which JVM automatically manages memory, avoiding manual memory management by identifying and freeing objects that are no longer in use. 1. GC uses accessibility analysis to determine the survival of objects, with heap as the main recycling area; 2. Java heap is divided into the Cetacean and the Old Age. The Cetacean includes the Eden area and the two Survivor areas. Most objects are allocated in the Eden area. MinorGC cleans up the area and copies the surviving objects to the Survivor area. Long-term surviving objects enter the old age; 3. Mainstream GC algorithms include mark-clearing, copying (for the Cetacean), mark-tissue (for the elderly); 4. Commonly used collectors include SerialGC, ParallelScavenge, CMS,

Jul 07, 2025 am 01:07 AM

Tools and Techniques for Profiling Java Application Performance

Java application performance tuning should rely on tools and data rather than guesswork. 1. Use JVM's own tools such as jstat to analyze GC, jstack to troubleshoot thread problems, and jmap and MAT analyze memory leaks; 2. Visual tools such as JProfiler, YourKit, and VisualVM can intuitively view the time-consuming of calling links and methods; 3. APM tools such as SkyWalking, Pinpoint, and NewRelic support full-link monitoring and distributed tracking; 4. Combining logs and Prometheus Grafana to achieve indicator monitoring and trend warning. Choosing tools rationally and understanding the results is key.

Jul 07, 2025 am 01:05 AM

Utilizing Java Generics for Enhanced Type Safety

Javagenericsareapowerfulfeaturethatallowsyoutowriteflexible,reusablecodewithoutsacrificingtypesafety.Insteadofwritingseparateclassesormethodsfordifferentdatatypes,youcancreategenericonesthatworkwithanytype—whilestill

Jul 07, 2025 am 12:56 AM

Using Java Future for Asynchronous Operations

Java's Future interface executes and obtains results through asynchronous tasks. Common methods include: 1. Submit a task to obtain a Future instance; 2. Call get() to block the result or set a timeout to avoid blocking; 3. Cancel the task through cancel() and use isCancelled() to judge the status; 4. Capture the ExecutionException to handle exceptions; 5. Manually coordinate the results of multiple Future merging, but does not support chain operations.

Jul 07, 2025 am 12:33 AM