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Java Concurrency in Practice: A Modern Approach

Use java.util.concurrent as the basis, Java21's Executors.newVirtualThreadPerTaskExecutor() is preferred to handle high-throughput I/O tasks; 2. Follow the principles of immutable objects and thread safety design, avoid sharing mutable states, and use record to define immutable data; 3. Use high-level abstracts such as CompletableFuture and StructuredConcurrency to replace low-level primitives such as synchronized/wait/notify; 4. Make good use of JFR, JMC and thread dumps for concurrency diagnosis, and discover thread hunger in time

Jul 24, 2025 am 02:30 AM

How to sleep a thread in Java?

The easiest way to get a thread to pause execution in Java is to use the Thread.sleep() method. This method causes the current thread to enter a blocking state and pauses the execution of the specified time (in milliseconds or nanoseconds), such as Thread.sleep(1000) means sleeping for 1 second; 1. This method must be placed in the try-catch block to handle InterruptedException; 2. It only affects the current thread, not other threads, and is suitable for multi-threaded environments; 3. It is often used to simulate delays, control loop frequency, and avoid frequent access to resources; 4. The sleep time is inaccurate and is affected by operating system scheduling; 5. Alternative solutions include wait()/notify() and TimeUni

Jul 24, 2025 am 02:30 AM

Connecting to Databases with Java (JDBC)

Make sure to add the JDBC driver of the corresponding database and configure project dependencies; 2. Use the DriverManager.getConnection() method to establish a connection through JDBCURL, username and password; 3. Use Statement or PreparedStatement to execute SQL queries and process ResultSet results; 4. Follow best practices such as using try-with-resources to automatically close resources, use PreparedStatement to prevent SQL injection, properly manage credentials and use connection pools, so as to achieve safe and efficient interaction between Java applications and databases.

Jul 24, 2025 am 02:08 AM

jdbc

Migrating a Legacy Java Application to Java 17 LTS

Evaluate the current status: confirm the JDK version, update the build tool plug-in, analyze dependency compatibility and use jdeps to detect internal API usage; 2. Handle destructive changes: remove discarded functions such as Applets, deal with strong encapsulation restrictions and temporarily open the module or refactor it into a public API through --add-opens; 3. Update the build configuration: Maven set maven.compiler.release=17, Gradle specifies the Java17 toolchain and upgrades to JUnit5; 4. Continuous testing: Run unit and integration tests, gradually introduce new features such as text blocks, pattern matching and Record to ensure stability, and ultimately achieve a safe and efficient Java17 migration.

Jul 24, 2025 am 02:01 AM

how to parse a string to a date in java

There are two main ways to parse strings as dates in Java: use SimpleDateFormat (for Java7 and below) and DateTimeFormatter (recommended for Java8). 1. When using SimpleDateFormat, you need to define the format string and create an instance. Use parse() method to convert the string into a Date object, but you should pay attention to its thread unsafe characteristics; 2. When using DateTimeFormatter, combine LocalDate or LocalDateTime to achieve a safer and modern parsing method; 3. Before parsing, you should ensure that the format matches, and it is recommended to pass regular verification or try-catc

Jul 24, 2025 am 01:57 AM

java 日期解析

Java Logging Best Practices with SLF4J and Logback

Use SLF4J instead of Logback to ensure portability; 2. Replace string splicing with parameterized logs to improve performance; 3. Use TRACE/DEBUG/INFO/WARN/ERROR levels reasonably; 4. Structured logs through MDC for machine resolution; 5. Avoid recording sensitive information such as passwords or PII; 6. Configure AsyncAppender to prevent blocking the main thread; 7. Test log output with ListAppender - Following these practices can make the log truly serve development and operation and maintenance, rather than creating noise.

Jul 24, 2025 am 01:55 AM

What is a Semaphore in Java concurrency?

AsemaphoreinJavaisasynchronizationtoolthatcontrolsaccesstosharedorlimitedresourcesthroughacquire()andrelease()operations.Itworksbymaintainingacountofpermits;threadsmustacquireapermitbeforeaccessingtheresource,andreleaseitafterward.1.Binarysemaphoresh

Jul 24, 2025 am 01:54 AM

java concurrency

how to get current date and time in java

There are three main ways to get the current time in Java: 1. Use java.util.Date to be suitable for simple scenarios. Use newDate() to get the current time and match SimpleDateFormat format; 2. It is recommended to use java.time.LocalDateTime introduced by Java8, and obtain the current time through LocalDateTime.now(), which supports flexible formatting and time zone processing; 3. Get time information with time zones recommended to use ZonedDateTime combined with ZoneId, such as ZonedDateTime.now(ZoneId.of("Asia/Shangh

Jul 24, 2025 am 01:53 AM

java date time

How to compile and run a Java program from the command line?

Yes, you can compile and run Java programs using the command line. First, make sure that the JDK is installed and verify the installation through javac-version and java-version; then create or locate the source code file ending in .java, such as HelloWorld.java; then use javacHelloWorld.java to compile and generate the .class file; finally run the program through javaHelloWorld (without the .class extension) to see the output result. It is necessary to pay attention to common problems such as the class name and file name, the main method is correct, and the processing of the package structure.

Jul 24, 2025 am 01:37 AM

Java Aspect-Oriented Programming (AOP) with AspectJ

To implement AOP programming in Java using AspectJ, you need to clearly define the sections, write point-cut expressions, master the recommended usage of Around, and choose the appropriate weaving method. When defining a section, create a class and add @Aspect annotation, specify the notification type with @Before, @After, etc., and define the interception range through the execution expression; it is recommended to start with a simple writing method, such as execution(com.example.service..*(..)) means to intercept all methods under the specified package, or combine conditions with annotations or logical operators; Around suggests that the most powerful, you need to call joinPoint.proceed(

Jul 24, 2025 am 01:35 AM

Building a Production-Ready RESTful API in Java

Use SpringBoot for rapid production-level settings, and use automatic configuration and embedded server to simplify development; 2. Verify inputs through BeanValidation, and use @ControllerAdvice to handle exceptions globally and return structured error messages; 3. Use JWT to combine SpringSecurity to achieve authentication and authorization, configure HTTPS and security headers to avoid hard-coded keys; 4. Integrate SLF4J, Micrometer, Prometheus and OpenTelemetry to implement logs, monitoring and link tracking, and expose health checks and indicator endpoints through actuator; 5. Use SpringDataJP

Jul 24, 2025 am 01:34 AM

java

Building Resilient Java Systems with Circuit Breakers

CircuitbreakersinJavaapplicationsmanagefailuresfromexternalservicesbytrippingwhenfailurethresholdsareexceeded,preventingcascadingoutages.1.Theyoperateinthreestates:Closed(normaloperation),Open(tripped,blockingrequests),andHalf-Open(testingservicereco

Jul 24, 2025 am 01:22 AM

Java AOT Compilation with GraalVM Native Image

GraalVMNativeImage is a technology that compiles Java applications into native machine code in advance, with faster startup speed and lower memory footprint. 1. It generates executable files through static analysis without the need for a JVM running environment; 2. The construction steps include installing GraalVM, installing native-image plug-in, preparing executable JAR and running native-image commands; 3. Pay attention to the characteristics of reflection, dynamic proxy, etc. that require manual configuration or tool support; 4. It is recommended to use a lightweight framework and control dependencies to improve construction efficiency and compatibility.

Jul 24, 2025 am 01:03 AM

how to round a double to 2 decimal places in java

In Java, there are three common methods for rounding double type values to two decimals: 1. Use Math.round() to simply round, and implement it by multiplying by 100, rounding and then dividing by 100. It is suitable for basic operations but cannot control the rounding mode; 2. Use DecimalFormat to format the output, suitable for display to users, format can be defined and localized, but the result is a string that is not suitable for subsequent calculations; 3. BigDecimal should be used for financial or high-precision requirements scenarios, providing complete rounding mode control to avoid floating point errors, but the syntax is more cumbersome. It is crucial to choose the right method according to actual needs. Misuse of errors can lead to accuracy problems or implicit errors.

Jul 24, 2025 am 12:54 AM