Java Date Format with Day Period: Pattern B Examples
Java date format with day period using pattern B in DateTimeFormatter (Java 16+). Print in the morning or at night, parse it and set custom ranges.
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Lokesh Gupta
Website: https://howtodoinjava.com
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My Articles:
Java Math.divideExact(): Detect Integer Division Overflow
Learn how Math.divideExact() in Java detects the Integer.MIN_VALUE / -1 overflow, how it handles zero, and how it compares to floorDivExact().
Java Math.abs() vs Math.absExact(): Overflow Explained
Java Math.abs() vs Math.absExact() with examples. Why Math.abs(Integer.MIN_VALUE) is negative, when absExact() throws, and safe alternatives.
Java String Concatenation Performance: + vs StringBuilder
Java string concatenation performance on JDK 25 with JMH results, how + compiles since JEP 280, why += in loops is slow, and concat() vs StringBuilder.
Java Text Block Formatting with Variables and Placeholders
Java text block formatting with variables using formatted(), String.format(), MessageFormat and named placeholders, plus what happened to string templates.
Java Multiline String: Text Blocks and Older Options
Write a Java multiline string with text blocks, control indentation, line breaks and trailing spaces, and see the String.join() options for Java 8 to 14.
Create Online Python Editor using Flask, Docker and K8s
Learn to build an online Python editor (using Flask, Docker, and Kubernetes) that allows users to write and run Python code directly from the browser.
Python List Comprehension: if-else, Nested and Examples
Learn Python list comprehension syntax with examples. Place if and if-else correctly, flatten lists, pair two lists with zip() and build dicts and sets.
OpenAI Fine-Tuning: Workflow, Examples and Availability
In this chatGPT tutorial, explore the entire life cycle of fine-tuning models from preparing training data, creating a fine-tuned model, and using it programmatically.
OpenAI API with Python: Setup and Chat Completions Example
Learn the basics of ChatGPT, the ChatGPT API for Python, and how to use it for creating and performing NLP tasks with examples.
Spring 6 Programmatic Validator: A Comprehensive Guide
Spring 6 Programmatic Validator API allows to add fine-grained validation rules beyond the capabilities of annotations-based declarative approach.
Spring 6 JdbcClient: When and How to Use it?
Since Spring 6.1, JdbcClient provides a unified client API for JDBC query and update operations, offering a more fluent and simplified interaction model.
Big O Notation: Measuring the Algorithm Efficiency
Big O notation categorizes the efficiency of a given algorithm and describes the upper bound of the growth rate of a function as the input grows.
Java Thread Dump: Capture with jcmd, jstack and Analyze It
Capture a Java thread dump with jcmd, jstack, kill -3 or JSON for virtual threads, read every line and find deadlocks, CPU hogs and stuck pools.
Hibernate Soft Delete: @SoftDelete Example and Strategies
Soft delete rows with Hibernate’s @SoftDelete: see the UPDATE that replaces DELETE, choose the DELETED, ACTIVE or TIMESTAMP strategy, read and restore deleted rows with native SQL, and avoid unique constraint errors.
Spring WebClient Retry and RetryWhen (with Examples)
Learn to retry the failed requests with Spring WebClient’s retry() and retryWhen() operators including retry on specific exception cases.
Running JUnit Tests with Gradle
By utilizing the –tests option, we can run unit tests using Gradle from entire test suites to specific test classes or methods.
Non-Static @BeforeAll and @AfterAll in JUnit (PER_CLASS)
Make JUnit @BeforeAll and @AfterAll non-static with @TestInstance(PER_CLASS). Project default, @MethodSource, @Nested, shared state and parallel tests.
Spring Bean Naming: Default, Explicit and Custom Strategies
In Spring, the default naming strategy utilizes the named of annotated classes or methods. Learn to customize it by explicit or custom naming with examples.
SpringExtension for JUnit 5: Why Do We Need It?
SpringExtension integrates the Spring TestContext Framework into JUnit 5 Jupiter extension model, sets up the ApplicationContext, and manages dependencies.
[Solved] Maven: release version 25 not supported (Java 21+)
The Maven error “release version 25 not supported” (or 21, 27) means the JDK that runs javac is older than maven.compiler.release. Learn how to check it with mvn -v and fix it with JAVA_HOME, toolchains, IntelliJ IDEA, GitHub Actions, Docker or Gradle, plus the maven-compiler-plugin setup for Java 21 and 25.
Spring Boot Transaction-Aware Caching Example
In Spring tutorial explores transaction-aware caching using transactionAware property and TransactionAwareCacheManagerProxy class with example.
Create and Extract a JAR File on Linux, macOS and Windows
Create and extract a JAR file with the jar command on Linux, macOS and Windows. Cheat sheet, runnable JARs, manifest, –dir and unzip options.
Install OpenJDK on Linux, macOS and Windows (Java 25)
Install OpenJDK 25 on Linux, macOS and Windows with apt, dnf, Homebrew, winget or SDKMAN. Pick a build, set JAVA_HOME and verify java -version.
List and Filter Docker Containers: A Cheat Sheet
Learn to list Docker containers, customizing the output format and filtering containers based on their running/stopped status and names, etc.
Align Text in Columns in Java: Print a Table with printf
Align text in columns in Java with printf widths, widths computed from the data, cut long values and a small TextTable class that prints Markdown tables.
Run a Spring Boot and Postgres Application on Podman
This guide explores the step-by-step process of containerization and running a Spring Boot application with PostgreSQL database using Podman.
Spring Boot REST API Timeout (with Examples)
Learn to handle REST API timeouts on the server side using Spring boot MVC async, Resilience4j, @Transactional, RestTemplate and WebClient with examples.
Convert JSON Array to List in Java: Jackson, Gson, Org.json
Convert JSON array to list in Java with Jackson 3 TypeReference, Gson TypeToken and Org.json, including records, unknown fields and large files.
Java Unnamed Variables and Patterns: Using _ (Java 22+)
Use Java unnamed variables and patterns with _ in catch blocks, lambdas, loops and record patterns, and see where the underscore is a compile error.
Java Scoped Values Explained with Examples (Java 25)
Java scoped values are final in Java 25. Learn ScopedValue.where().run(), call(), rebinding, child threads and how scoped values compare with ThreadLocal.
Spring Cloud AWS SQS: SqsTemplate and @SqsListener Example
Learn to send and receive Amazon SQS messages in a Spring Boot app with Spring Cloud AWS: SqsTemplate, @SqsListener, the endpoint property for LocalStack, processing more than 10 messages concurrently with maxConcurrentMessages, acknowledgement modes and FIFO queues.
Kafka with Schema Registry and Avro Serialization
Learn to integrate Kafka with Apache Avro and Schema Registry to manage the changes in Schema over time, and a demo to test this integration.
Git Interview Questions and Answers for DevOps Roles
Top 30+ Git interview questions and answers providing a thorough exploration of essential concepts and practices within the Git version control system.
Java Math.ceil() vs floor() vs round() With Examples
Math.ceil() vs floor() vs round() in Java explained with negative numbers, ties, return types, ceilDiv(), NaN edge cases and a rating example.
Spring vs. Spring Boot: What’s Difference?
This Spring vs. Spring Boot tutorial lists the differences between Spring framework and Spring Boot based on general characteristics and features.
Spring Boot OpenFeign Client Tutorial
Learn about Feign Client and how to use it in a Spring Boot application. Also, learn the commonly used default Feign configurations and customizing them.
Iterator vs ListIterator vs Spliterator in Java (+ Enumeration)
Iterator vs ListIterator vs Spliterator in Java compared in one table, with Enumeration, fail-fast rules, examples and when to use each cursor.
Python Numpy 101: A Beginners Guide
Learn NumPy basic concepts, constants, attributes and how to use NumPy for data visualization, followed by the advantages and limitations.
TypeScript Exception Handling: try/catch and Custom Errors
TypeScript exception handling uses try, catch, finally and throw, with an unknown catch variable under strict. Examples cover custom Error classes, cause, instanceof and async errors.
TypeScript map vs flatMap: Array Differences and Examples
The map() method returns one result per element, while flatMap() can return zero, one or many and flattens them one level. Tested examples on TypeScript 7.0.2.
TypeScript Record vs Map: Differences and When to Use Each
A Record types a plain object; a Map is a runtime collection. Compare them on keys, order, JSON, type checks and user input, and convert one into the other.
TypeScript Record: Check Keys, Iterate and Type Objects
Record
Spring WebMvcConfigurer: Customize Default MVC Configurations
Learn to use Spring WebMvcConfigurer to customize various aspects of Spring MVC, such as argument resolvers, view resolvers, exception handling, and more.
TypeScript vs JavaScript: Key Differences with Examples
TypeScript checks types at compile time and outputs plain JavaScript; JavaScript checks them only at runtime. A side-by-side comparison with real compiler errors.
Tracking @Entity Creation and Updation Timestamps
Learn to track or audit the @Entity creation and updation timestamps using Spring Data annotations, JPA lifecycle callbacks, Hibernate and Envers library.
Spring Boot WebClient POST Example
Spring Boot WebClient example discusses sending HTTP POST requests, submitting form data and handling the response status, headers and body.
Displaying Images with Thymeleaf and Spring Boot
Learn to display images from different sources (e.g., resources directory or database) using the Thymeleaf view templates in a Spring Boot application.
Spring Boot Hello World Example: Beginners Guide
Spring Boot is an open-source framework that simplifies the development of stand-alone, production-grade Spring-based MVC applications and microservices.
Java Records in JPA/Spring Data: Challenges and Usecases
Java records cannot be used as the replacement for JPA entities because they restrict the byte code manipulation, generally required by frameworks to work.