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Multi level grouping with streams


1. Introduction With Java 8 streams it is pretty easy to group collections of objects based on different criteria. In this post, we will see how we can make from simple single level groupings to more complex, involving several levels of groupings. We will use two classes to represent the objects we want to group by: person and pet. Person.class ...

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Neo4j: A procedure for the SLM clustering algorithm


In the middle of last year I blogged about the Smart Local Moving algorithm which is used for community detection in networks and with the upcoming introduction of procedures in Neo4j I thought it’d be fun to make that code accessible as one. If you want to grab the code and follow along it’s sitting on the SLM repository on ...

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Parallel execution of blocking tasks with RxJava and Completable


” How parallel execution of blocking “side-effect only” (aka void) tasks became easier with Completable abstraction introduced in RxJava 1.1.1. “ As you may have noticed reading my blog I primarily specialize in Software Craftsmanship and automatic code testing. However, in addition I am an enthusiast of Continuous Delivery and broadly defined concurrency. The last point ranges from pure threads ...

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NetBeans Java EE Tip #3: RESTful Web Services from Database


Many modern web applications are moving towards the use of stateless communications using HTTP.  The REST (Representational State Transfer) architectural style is oftentimes utilized to design networked applications, and with Java EE 7 it is very easy to develop a RESTful backend for database communication.  Using a simple POJO (plain old Java object), one can provide a complete solution for ...

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Docker Installation Scripts – CLI, Machine, Compose, Version Manager


Docker Toolbox is cool! It is a single point download that gives you everything to get started with Docker. But it comes with other tools like VirtualBox and Kitematic which you may not want. So what do you do? You install the tools that you like using CLI. This blog shows how to do exactly that. All the commands are installed in the /usr/bin/local directory. ...

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Kotlin Month Post 1: Assorted Features


To open up Kotlin Month, we’ll look at a small assortment of Kotlin’s features that aren’t big enough to merit their own post and don’t fit into a grouping for the upcoming posts, starting with operator overloading. Operator Overloading Because of the mess it made in C++, Java decided to not include operator overloading, and it has unfortunately stuck to ...

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AWS SQS and Spring JMS integration


Amazon WEB Services provide us with the SQS messaging service. The java sdk for sqs is compatible with JMS. Therefore instead of using SQS as a simple spring bean we can integrate it with the JMS integration framework that spring provides. I will use spring-boot and gradle. The gradle file: group 'com.gkatzioura.sqstesting' version '1.0-SNAPSHOT' buildscript { repositories { mavenCentral() } ...

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A Very Peculiar, but Possibly Cunning Kotlin Language Feature


This has caught me by surprise. After studying the Kotlin language to learn about how to best leverage this interesting new language for jOOQ, I stumbled upon this puzzler. What do you think the following program will print? fun main(args: Array) { (1..5).forEach { if (it == 3) return print(it) } print("done") } Well… You might have guessed wrong. The ...

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