Hazelcast’s MapLoader pitfalls

One of the core data structures provided by Hazelcast is IMap<K, V> extendingjava.util.concurrent.ConcurrentMap – which is basically a distributed map,…

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Property-based testing with Spock

Property based testing is an alternative approach to testing, complementing example based testing. The latter is what we’ve been doing…

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URL shortener service in 42 lines of code in… Java (?!) Spring Boot + Redis

Apparently writing a URL shortener service is the new “Hello, world!” in the IoT/microservice/era world. It all started with A…

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Testing code for excessively large inputs

When writing unit tests we mostly focus on business correctness. We do our best to exercise happy path and all…

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Grouping, sampling and batching – custom collectors in Java 8

Continuing first article, this time we will write some more useful custom collectors: for grouping by given criteria, sampling input, batching…

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Building extremely large in-memory InputStream for testing purposes

For some reason I needed extremely large, possibly even infinite InputStream that would simply return the samebyte[] over and over. This way I…

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Introduction to writing custom collectors in Java 8

Java 8 introduced the concept of collectors. Most of the time we barely use factory methods from Collectors class, e.g. collect(toList()), toSet() or maybe something…

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Turning recursive file system traversal into Stream

When I was learning programming, back in the days of Turbo Pascal, I managed to list files in directory usingFindFirst, FindNext and FindClose functions.…

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Option.fold() considered unreadable

We had a lengthy discussion recently during code review whether scala.Option.fold() is idiomatic and clever or maybe unreadable and tricky?…

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