Recent content on A day of coding

 
 As the forklifts break through the wall, the Elves are delighted to discover that there was a cafeteria on the other side after all. 
 -- Day 5 - Advent of Code 2025 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Day 5 revolves around interpreting ranges of ingredient IDs and determining which IDs are considered fresh. The input is split into two…

 
 You ride the escalator down to the printing department. They’re clearly getting ready for Christmas; they have lots of large rolls of paper everywhere, and there’s even a massive printer in the corner (to handle the really big print jobs). 
 -- Day 4 - Advent of Code 2025 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Day 4 of the…

 
 You descend a short staircase, enter the surprisingly vast lobby, and are quickly cleared by the security checkpoint. When you get to the main elevators, however, you discover that each one has a red light above it: they’re all offline . 
 “Sorry about that,” an Elf apologizes as she tinkers with a nearby control panel. “Some kind of electrical surge seems…

 
 You get inside and take the elevator to its only other stop: the gift shop. “Thank you for visiting the North Pole!” gleefully exclaims a nearby sign. You aren’t sure who is even allowed to visit the North Pole, but you know you can access the lobby through here, and from there you can access the rest of the North Pole base. 
 -- Day 2 - Advent of Code 2025

 
 You arrive at the secret entrance to the North Pole base ready to start decorating. Unfortunately, the password seems to have been changed, so you can’t get in. A document taped to the wall helpfully explains: 
 “Due to new security protocols, the password is locked in the safe below. Please see the attached document for the new combination.” 
 -- Day 1 -…
Manually releasing a Maven package is a hassle—updating versions, tagging commits, building artifacts, and pushing them to a package repository. What if you could automate most of this from GitHub Actions? 
 In this guide, we’ll set up a workflow that builds the project, bumps the release version, creates a git tag, and opens a draft GitHub release—without hand-editing pom.xml on every cut.…
When response times spike or a request fails deep in a distributed system, guessing is expensive. OpenTelemetry gives you a vendor-neutral way to collect traces, metrics, and logs so you can see where time is spent and what broke. 
 In this post, we’ll wire OpenTelemetry into a Java application: dependencies, manual SDK setup, wrapping work in spans, and exporting data so bottlenecks show up…

 
 The Historians are quite pixelated again. This time, a massive, black building looms over you - you’re right outside the CPU! 
 While The Historians get to work, a nearby program sees that you’re idle and challenges you to a race . Apparently, you’ve arrived just in time for the frequently-held race condition festival! 
 -- Day 20 - Advent of Code 2024 
…

 
 Today, The Historians take you up to the hot springs on Gear Island! Very suspiciously , absolutely nothing goes wrong as they begin their careful search of the vast field of helixes. 
 -- Day 19 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Part 1 
 The solution for part 1 today can be resolved by creating a regular…

 
 You and The Historians look a lot more pixelated than you remember. You’re inside a computer at the North Pole! 
 -- Day 18 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Today the assignment involves yet another grid and pathfinding algorithm. So to read the input into memory I created this small method. 
 1 public void…

 
 The Historians push the button on their strange device, but this time, you all just feel like you’re falling . 
 -- Day 17 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Part 1 
 The first thing for today is modelling Opcode and the ComputeEngine . Where the compute engine represents the machine that is executing the…

 
 It’s time again for the Reindeer Olympics ! This year, the big event is the Reindeer Maze , where the Reindeer compete for the lowest score . 
 -- Day 16 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Part 1 
 Since the problem statement clearly indicates that a path solving algorithm would be best suited I decided to…

 
 One of The Historians needs to use the bathroom; fortunately, you know there’s a bathroom near an unvisited location on their list, and so you’re all quickly teleported directly to the lobby of Easter Bunny Headquarters. 
 -- Day 14 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Since the input is a robot I already…

 
 Next up: the lobby of a resort on a tropical island. The Historians take a moment to admire the hexagonal floor tiles before spreading out. 
 Fortunately, it looks like the resort has a new arcade ! Maybe you can win some prizes from the claw machines ? 
 -- Day 13 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 First I created…

 
 You’re about to settle near a complex arrangement of garden plots when some Elves ask if you can lend a hand. They’d like to set up fences around each region of garden plots, but they can’t figure out how much fence they need to order or how much it will cost. They hand you a map (your puzzle input) of the garden plots. 
 -- Day 12 - Advent of Code 2024

 
 The ancient civilization on Pluto was known for its ability to manipulate spacetime, and while The Historians explore their infinite corridors, you’ve noticed a strange set of physics-defying stones. 
 -- Day 11 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Part 1 
 For today the first step is writing a recursive method…

 
 You all arrive at a Lava Production Facility on a floating island in the sky. As the others begin to search the massive industrial complex, you feel a small nose boop your leg and look down to discover a reindeer wearing a hard hat. 
 -- Day 10 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Part 1 
 The first step of today is…

 
 Another push of the button leaves you in the familiar hallways of some friendly amphipods ! Good thing you each somehow got your own personal mini submarine. The Historians jet away in search of the Chief, mostly by driving directly into walls. 
 -- [Day 9 - Advent of Code 2024[( https://adventofcode.com/2024/day/9 ) 
 
 Solution in Java 
 Full source can be found: in…

 
 You find yourselves on the roof of a top-secret Easter Bunny installation. 
 While The Historians do their thing, you take a look at the familiar huge antenna . Much to your surprise, it seems to have been reconfigured to emit a signal that makes people 0.1% more likely to buy Easter Bunny brand Imitation Mediocre Chocolate as a Christmas gift! Unthinkable! 
 -- Day 8 - Advent…
Day 7 assignment 
 
 
 The Historians take you to a familiar rope bridge over a river in the middle of a jungle. The Chief isn’t on this side of the bridge, though; maybe he’s on the other side? 
 -- Day 7 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 For today I setup a small little interface Instruction to capture…
Day 6 assignment 
 
 
 The Historians use their fancy device again, this time to whisk you all away to the North Pole prototype suit manufacturing lab… in the year 1518 ! It turns out that having direct access to history is very convenient for a group of historians. 
 You still have to be careful of time paradoxes, and so it will be important to avoid anyone from 1518 while…
Day 5 assignment 
 
 
 Satisfied with their search on Ceres, the squadron of scholars suggests subsequently scanning the stationery stacks of sub-basement 17. 
 The North Pole printing department is busier than ever this close to Christmas, and while The Historians continue their search of this historically significant facility, an Elf operating a very familiar printer beckons you…
Day 4 assignment 
 
 
 “Looks like the Chief’s not here. Next!” One of The Historians pulls out a device and pushes the only button on it. After a brief flash, you recognize the interior of the Ceres monitoring station ! 
 -- Day 3 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Part 1 
 For the first part of…
Day 3 assignment 
 
 
 “Our computers are having issues, so I have no idea if we have any Chief Historians in stock! You’re welcome to check the warehouse, though,” says the mildly flustered shopkeeper at the North Pole Toboggan Rental Shop . The Historians head out to take a look. 
 Day 3 - Advent of Code 2024 
 
 Solution in Java 
 Full source can be…
Day 2 assignment 
 
 
 Fortunately, the first location The Historians want to search isn’t a long walk from the Chief Historian’s office. 
 While the Red-Nosed Reindeer nuclear fusion/fission plant appears to contain no sign of the Chief Historian, the engineers there run up to you as soon as they see you. Apparently, they still talk about the time Rudolph was saved…
Day 1 assignment 
 
 
 The Chief Historian is always present for the big Christmas sleigh launch, but nobody has seen him in months! Last anyone heard, he was visiting locations that are historically significant to the North Pole; a group of Senior Historians has asked you to accompany them as they check the places they think he was most likely to visit…. 
 -- Day 1 - Advent…
In Java we have the option to add or change the code we are compiling during compilation. It allows us to add new code based upon annotations in the code. This could for example be used to generate some proxy classes, or setting up some service loader files. 
 In this post we will be looking at annotation processing to create a light-weight and very simplistic bean context. 
 Note: if you…

 
 As you try to figure out what to do next, you notice a poster on a wall near the ferry dock. “Boat races! Open to the public! Grand prize is an all-expenses-paid trip to Desert Island !” That must be where the sand comes from! Best of all, the boat races are starting in just a few minutes. 
 -- Day 6 - Advent of Code 2023 
 
 Solution in Java 
 Full source…

 
 “Oh, we had to stop the water because we ran out of sand to filter it with! Can’t make snow with dirty water. Don’t worry, I’m sure we’ll get more sand soon; we only turned off the water a few days… weeks… oh no.” His face sinks into a look of horrified realization. 
 -- Day 5 - Advent of Code 2023 
 
 Solution in Java 
…

 
 Tell you what: if you can help me with something quick, I’ll let you borrow my boat and you can go visit the gardener. I got all these scratchcards as a gift, but I can’t figure out what I’ve won." 
 -- Day 4 - Advent of Code 2023 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Part 1 
 I created a class Card to represent the…

 
 You and the Elf eventually reach a gondola lift station; he says the gondola lift will take you up to the water source , but this is as far as he can bring you. You go inside. 
 It doesn’t take long to find the gondolas, but there seems to be a problem: they’re not moving. 
 -- Day 3 - Advent of Code 2023 
 
 Solution in Java 
 Full source can be found:…

 
 You’re launched high into the atmosphere! The apex of your trajectory just barely reaches the surface of a large island floating in the sky. You gently land in a fluffy pile of leaves. It’s quite cold, but you don’t see much snow. An Elf runs over to greet you. 
 -- Day 2 - Advent of Code 2023 
 
 Solution in Java 
 Full source can be found: in GitHub…

 
 Something is wrong with global snow production, and you’ve been selected to take a look. The Elves have even given you a map; on it, they’ve used stars to mark the top fifty locations that are likely to be having problems. 
 -- Day 1 - Advent of Code 2023 
 
 Solution in Java 
 Full source can be found: in GitHub 
 Part 1 
 In the first part of this…
When developing in PHP you may have encountered the following problem: 
 
 During an upgrade of the code, or just a minor bug fix, you have introduced new (non critical-error) code. This is causing PHP to crash and report ugly warnings to the user. 
 
 Well I think most developers of PHP have found this problem. One option, which is always done on live servers, is setting the…
I’ve been working on a quiz section for one of my websites lately, well tried to anyway. One of the dumbest things happened. In a quiz you want to randomly pick questions and serve them to the visitor. That way they can answer them and shout WAHOO once they have one right. 
 Problem I had was that I couldn’t figure out how to sort all the questions in a completely random order, well semi…
All software developers have to deal with it. Version control software. Today I decided to play a bit with installing my own dedicated SVN (subversion) server. This, hopefully brief, step plan will help you do the same. 
 Downloading all needed software 
 Before you can continue with the tutorial you will have to get the following things: 
 
 A ‘virtual’ computer to install you…
I’ve recently gotten a few questions on the issue of multilingual website implementation and the usage of a language indicator (eg: nl, uk, de). So today it’s time to look into best practice, both from the visitors point of view as well as that of the programmer. 
 Visitors like confirmation 
 That was easy. I just summed up the reason why it could be important for your visitor to include…
Strange title isn’t. Is there such a thing as basic SQL (Structured Query Language). Lets try and find out. I will be covering some basics, thus creating a simple table. Making some basic queries and basics on T-SQL (Transact SQL). 
 Why use databases 
 Best to begin with a little story I suppose. Why would you want to use a database? Well it’s pretty easy. Databases give you the…
Hi, I’m Gerben Jongerius — a Java consultant based in Roermond, the Netherlands. I develop complex back-end systems . 
 I’m currently a principal consultant at Open Circle Solutions , on assignment as a Java developer at Energie Data Services Nederland (EDSN) . Before that I spent several years as a Java consultant at group9 , with longer assignments at ASML and APG. 
 Experience 
…