Optional Is a Law-breaking Monad but a Good Type

In most programming languages empty-or-not-empty types are well-behaved monads. (Yes, I used the M-word — don’t worry, no math.) This means their mechanics fulfill a couple of definitions and follow a number of laws that guarantee safe…

Approval Testing

Have you ever written an assert statement like “assertEquals(“”, functionCall())? I mean where functionCall() is going to return a String…

Ten Must Ask Questions for Data Engineering Projects

Think of this as a checklist of the questions that you need to ask before giving an estimate of when you will deliver, or when you will start design. Andyou definitely need to ask these questions before coding.

Using Optional — Nowhere, Somewhere, or Everywhere?

Java 8 introduced Optional for a very precise use case: to allow the continuation of Stream pipelines without triggering a NullPointerException. This is NPE-safe:

Stream.of(2, 4, 6)
    .filter(this::isOdd) //…

How to Crash Your JVM

There are so many new APIs, cool libraries, and must-try techniques you need to know that it can be hard to stay up to date.

But is this really all you need to know as a Java developer? What about the environment your software is running in? Couldn’t it be that a…

How to Provoke a Race Condition

You have a method used by multiple threads in a program. You suspect there’s a race condition, but the evidence is inconclusive. Nor does the evidence tell you what’s wrong.

Kinds of Comments

Assume you want to put some comments into your Java code. Do you use /**, /*, or //? And where exactly do you put them? Beyond syntax, there are established practices that attach semantics to which mechanism is used where.

Javadoc Comments for Contracts

Using Coverage to Improve Your Unit Tests

Measuring the coverage of your tests is easier than ever. In a modern IDE the button to run your tests with coverage is right next to the ones to run or debug them. The coverage results are presented class by class with little chart graphics, as well as…

Data Engineering for Autonomy and Rapid Innovation

In many organizations, data engineering is treated purely as a specialty. Data pipelines are seen as the complex, arcane domain of data engineers. Often data engineers are organized into dedicated teams, or embedded into vertically oriented…

Focus on Maintainability and Break Those ETL Tasks Up

When writing ETLs, we should ensure others are able to support and extend our work by breaking complex tasks into a chain of simple ones.