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Spring Boot HTTP Interface using @HttpExchange

Learn to use the Spring @HttpExchange to create and configure a declarative HTTP client interface (blocking/non-blocking) with examples.

Spring ProblemDetail and ErrorResponse

Starting since Spring 6 and Spring Boot 3, the Spring Framework supports the “Problem Details for HTTP APIs” specification, RFC 7807. This Spring tutorial will guide you through this new enhancement in detail. 1. Problem Details Specification [RFC 7807] This RFC defines simple JSON and XML document formats that can …

Getting Started with JHipster and Spring Boot

This JHipster tutorial will familiarize you with this popular code generation platform and work with front-end and backend generated code.

TypeScript – How to Remove Items from Array

Learn to remove or pop items from an array in TypeScript using pop(), shift(), splice(), filter() and delete operator with examples.

TypeScript – How to Add Items to Array

Learn to add or append or push new items into an array in TypeScript. Also, learn to append or merge an array into a specified array.

TypeScript Date

Learn to create new Date objects in TypeScript, and modify, compare and format them to custom and inbuilt locale-specific patterns.

JMH – Java Microbenchmark Harness

Java Microbenchmark Harness (JMH) is a tool that allows measuring various code performance characteristics and identifying bottlenecks with precision – up to the method level.

Spring @Lookup Method Injection

Spring lookup method injection is the container’s ability to override methods on container-managed beans and return another container-managed bean.

Spring: Injecting Prototype Bean into Singleton Bean

Spring context supports singleton and prototype bean scopes along with four other scopes specific to the web context. The singleton is the default bean scope. A common problem arises when we want to inject a prototype-scoped bean into a singleton-scoped bean. In this case, as the singleton bean is initialized …

Spring Boot 3 OpenAPI Docs with Springdoc and Swagger

By default, SpringDoc automatically generates docs in JSON/YAML formats. When Swagger UI is enabled, it uses it to generate the docs in HTML format, too.

Java Reserved and Contextual Keywords

Java has 51 reserved words and 16 contextual keywords that cannot be used as identifiers in the code. Programmers should not use these keywords for other purposes.

Java IO (Input/Output) Tutorials

Java IO is a collection of APIs targeted at reading and writing data from various sources to several targets. For example, we can read data from a file or over a network, write to a file or write a response back over the network. This page categorizes the various IO-related common tasks …

Spring Tutorials

Spring helps write high-performing, easily testable, and reusable code and promotes programming best practices by applying dependency injection (DI).

Spring MVC

Spring WebMVC (or Spring MVC) contains Spring’s model-view-controller (MVC) and REST Web Services implementation for web applications.

Spring Batch Tutorial

Spring batch is a lightweight, comprehensive framework designed for the development of robust batch processing applications. Learn with examples.

Java Queue: From Fundamentals to Mastery

Learn Queue data structure and the Java Queue interface and implementations with practical examples such as LinkedList, PriorityQueue and ArrayDeque.

JUnit 5 XML Report Example

Learn about the JUnit XML report generation in legacy and new open test reporting formats and switching a specific version using the configuration parameters.

What’s New in Spring 6 and Spring Boot 3

Learn about the new features and changes introduced in Spring 6 and Spring boot 3 such as baseline upgrade to Java 17 and removing all deprecated classes, methods and properties.

Java String Tutorial

Java String class examples. Learn to create strings, methods, comparisons, formatting and various conversions with simple and easy to follow Java examples.

How to Find a File in Directory in Java

Learn to find a file by name in a given directory and its sub-directories in Java and search up to a configured depth of sub-directories with examples.

Java 8 Stream – Collectors GroupingBy with Examples

Learn to use Collectors.groupingBy() method to group and aggregate the Stream elements similar to ‘GROUP BY‘ clause in the SQL. Stream -> groupingBy() -> Map of elements after applying ‘group by’ operation 1. Collectors.groupingBy() Method 1.1. Syntax The groupingBy() method returns a Collector implementing a “GROUP BY” operation on Stream …

Read a File from AWS S3 using S3Client

Learn to read a text file stored in AWS S3 bucket. We will learn to read a public file or non-public file using the access/secret keys.

Log4j2 Dynamic ThresholdFilter Example

Learn to configure log4j2 DynamicThresholdFilter and how to match thresholds and write the filtered messages using various combinations.

Log4j2 – Filter Messages using MarkerFilter

Learn to filter the logging messages or events using the Log4j2 MarkerFilter, create instances, and configure them in log4j2.xml.

[Solved] “Stream has already been operated upon or closed” Exception

Learned the root cause and solution of the Java Stream exception “IllegalStateException: stream has already been operated upon or closed”.

How to Flatten a Nested List in Java

Flattening a nested list may seem hard at the beginning, but it’s not. It can be easily done using only plain Java, streams, or external libraries.

Interview Guide

These articles will help you prepare for the next interview with more confidence. We have tried to put as much reasoning as possible in each question. Feel free to suggest more questions and guides. 1. Java Interview Questions 2. Spring Interview Questions 3. More Questions Happy Learning !!

Object Oriented Programming Tutorials

Object-oriented programming (OOP) is a programming model that organizes software design around data or objects. Learn how Java supports OOP.

How to Iterate Over a Stream With Indices

Java Streams have gained a lot of awareness and being able to iterate through with indices can be helpful. Learn a few ways with examples.

Spring Boot Filter: with Order and URL Pattern Examples

In this Spring boot tutorial, we will learn to create, order and register servlet filters in different ways including Filter interface, @WebFilter annotation and inbuilt filter bean classes. 1. Introduction In a web application, we must implement the javax.servlet.Filter interface (jakarta.servlet.Filter in Spring Boot 3) to create filters that can …

Maven Tutorials

Maven is a build tool based on POM and is generally used for Java projects to automatically download the project dependencies in build time.

Java – Remove/Update Elements From List using Stream

Learn to remove and update elements of a Collection using Stream.filter() and Strea,map() methods in Java with examples.

Running JUnit Tests with Maven

Learn to run JUnit tests using Maven Surefire Plugin. We will learn to run a single test, run only selected tests or run all the tests in the project.

Convert an Object to Map in Java

Learn to convert a given Java object into a Map using different solutions including Jackson ObjectMapper, Gson and Java reflection.

Jackson Error: Java 8 date/time type not supported by default

Learn to fix the error ‘Java 8 date/time type not supported by default’ while serializing and deserializing Java 8 Date time classes using Jackson.

How to Filter a Map by List of Keys in Java

Learn to filter a Java HashMap by List of keys and collect the matching entries into a submap or matching values in a List.

TypeScript Tutorial

TypeScript is an open-source programming language that was developed and maintained by Microsoft in 2012. TypeScript brings ‘types’ (or datatypes) to JavaScript making a strongly typed language. This page lists down all the TypeScript tutorials posted on this blog for easy navigation. 1. TypeScript Basics 2. TypeScript Types 3. TypeScript …

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Lokesh Gupta

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