JVM Languages

Introduction In Kotlin, classes do not have static methods. A Java equivalent semantic can be provided to callers using the concept of a companion object though. This post will go into details of what it takes to support a JUnit 5 @BeforeAll and @AfterAll annotation which depend on the precense of a static methods in test classes. BeforeAll and AfterAll in Java Junit ...

The object keyword in Kotlin creates singleton in a very convenient way. It can be used for example as a state of an operation. Spock Framework is one of the most expressive and readable test framework available in the Java ecosystem. Let’s see how Kotlin object can be used in the Spock tests. What do we want to test? We ...

Some people have spoken against Kotlin’s decision to make classes, methods, etc. public by default (when no visibility modifier is used), and I would just like to pitch in on why I think JetBrains made the right decision on this one. Those who are against it bring up the principle of hiding everything that you can get away with in ...

One of the questions my reader often ask me is, shall I learn Scala? Does Scala has better future than Java, or why Java developer should learn Scala and so on. Well, there can be many reasons for learning Scala e.g. you are forced to learn because it been used in the new company you joined or your solution architect ...

This post walks through a sample that demonstrates Kotlin’s ability to cleverly reify generic type parameters. So consider first a world where Kotlin does not support this feature, if we were using the Jackson library to convert a JSON to a Map with String based keys and Integer based values, I would use a code along these lines: @Test fun `sample ...

Depending on various projects, sometimes there is the need to execute some actions on initialization just before our application starts to serve requests. It was a common practice to call the functions that we wanted to get executed through GlobalSettings, however it is not recommended. The other way around to achieve this is to implement a class which will be ...

It is very simple to write a Tuple type with the expressiveness of Kotlin. My objective expressed in tests is the following: 1. Be able to define a Tuple of up to 5 elements and be able to retrieve the elements using an index like placeholder, in a test expressed with 2 elements like this: val tup = Tuple("elem1", "elem2") assertThat(tup._1).isEqualTo("elem1") assertThat(tup._2).isEqualTo("elem2") ...

Scala has a Try type to functionally handle exceptions. I could get my head around using this type using the excellent Neophyte’s guide to Scala by Daniel Westheide. This post will replicate this type using Kotlin. Background Consider a simple function which takes two String, converts them to integer and then divides them(sample based on scaladoc of Try) : fun ...

A few months ago, somebody in the office pointed us to an interesting  job offer from CartoDB which looked as follows: What follows is a technical test for this job offer at CARTO: https://boards.greenhouse.io/cartodb/jobs/705852#.WSvORxOGPUI Build the following and make it run as fast as you possibly can using Python 3 (vanilla). The faster it runs, the more you will impress us! ...