Jeff Martin and myself will speak at Java One (March 17-19, Redwood Shores, CA, USA) on Java and WebAssembly. Here is a $50 discount code if you register by Feb. 9: J12026SSM

https://horstmann.com/presentations/2026/javaone/JavaOne%20Speaker_Cay%20H.png

On Tuesday, February 10, Maurice Naftalin and myself will speak at Voxxed Days CERN on "Streams—Below the Surface". https://horstmann.com/presentations/2026/cern/Cay_Horstmann_Maurice_Naftalin.jpeg

Think you really know Java? ☕
Guess the Java version from code snippets in my Java Version Quiz: https://mostlynerdless.de/java-game/

"Java: To infinity and beyond" kicked off by Sharat Chander at Jfokus

#Community #Java #Jfokus

On the plane to Stockholm where I will give two presentations at JFokus (https://jfokus.se/speakers.html?showid=15121), on Project Valhalla and the Java Class File API.

@parttimenerd I don't get it. Why wouldn't it be legal for Java ≥ 10? The var isn't necessary, but Core Java says it's there if you want to attach annotations to the parameter while being coy about its type.

Java 1.0 was released on this day 30 years ago https://www.java.com/releases/ https://web.archive.org/web/20070310235103/http://www.sun.com/smi/Press/sunflash/1996-01/sunflash.960123.10561.xml #java #onthisday

AUSNAHMESTAPELÜBERWACHUNG!

(Wollte doch nur auswählen, wann meine neue Leiter geliefert werden soll 🥲)

This Thursday January 22, I will be speaking at the Dublin JUG and the JChampionsConference, on Java pattern matching + a bonus talk for in-person attendees.

If you are in Dublin, sign up here: https://ti.to/dublin-java-user-group/2601-jchampions-cay-horstmann. Start time 18:15 UTC

To follow online, sign up here: https://www.eventbrite.com/e/jchampions-conference-online-tickets-1977195901165. Start time 20:00 UTC

In case you're working with Java, I highly recommend the virtual JChampions Conference 2026 (https://jchampionsconf.com/ ) which will start on Jan 22. Have a look at the schedule, there are many great sessions by recognized Java champions. Get your free ticket at https://www.eventbrite.com/e/jchampions-conference-online-tickets-1977195901165
#java

The excellent free JChampions Conference 2026 (https://jchampionsconf.com) is happening online Thur 1/22/2026, Fri 1/23/2026, Mon 1/26/2026, and Tues 1/27/2026.
Get free tickets from Eventbrite: https://www.eventbrite.com/e/jchampions-conference-online-tickets-1977195901165

@tagir_valeev Java doesn't take final into account with extends, so it treats T as an unknown subtype of Integer. Thus it is unsurprising that t = t + 1 or t += 1 fails. Interesting that ++/-- work.

I just completed all 12 days of Advent of Code 2025! #AdventOfCode https://adventofcode.com/ 🎉 and can sleep in for the rest of the holiday season 🛌

I just completed "Reactor" - Day 11 - Advent of Code 2025 #AdventOfCode https://github.com/cayhorstmann/adventofcode2025/blob/main/Day11.java Added a "DAG path count" method to my graph utilities.

Here is my "Java Advent" article on nice and naughty cases of pattern matching, with nicer formatting than WordPress can muster, and the ability to leave comments without logging into WordPress: https://horstmann.com/unblog/2025-12-12/

I just completed "Factory" - Day 10 - Advent of Code 2025 #AdventOfCode https://github.com/cayhorstmann/adventofcode2025/blob/main/Day10.java The first time I ever used Z3. Very impressive.

@mina Hi, the difference was between 3 min or so, and, after being more clever about it, less than a second.

@timbray Wish them luck, but...how do you search right now? I used to think search is hard, but judging from Kagi, it doesn't take all that many paying customers (myself included) to do decent search.

I just completed "Movie Theater" - Day 9 - Advent of Code 2025 #AdventOfCode https://github.com/cayhorstmann/adventofcode2025/blob/main/Day9.java

It's that time of the year when I get baffled by polygons in a grid, where it makes a difference whether a corner goes up or down, and it's not even easy to tell which, when the grid is too large to put in a char[][] array. Today, I resolved to figure out the geometry once and for all. Did you know that you can tell from the shoelace formula whether the traversal is clockwise?

I participate in Advent of Code (https://adventofcode.com/) to learn, and today I learned plenty. My naïve brute force solution for Day 8 required 3 minutes. I re-learned the union-find algorithm (never touched it since grad school, 45 years ago), and am down to < 1 sec. https://github.com/cayhorstmann/adventofcode2025/blob/main/Day8.java