Slides From My Talk: Mutation Testing In Java

Few weeks ago I have a talk at conference called “33rd Degree 4 Charity” which was a 2 day event held in Wroclaw. These are my slides (there is no recording): Bitcoin for programmers - part 1 version 2 from Wojciech Langiewicz The related sample project that I used as a demo is here: If you are interested in this topic you’ll get most out of it if you clone the project, run it locally and analyze the results (everything is explained in the README.

How to put custom messages into Bitcoin blockchain - OP_RETURN

I have spent last few days looking very closely at OP_RETURN features. This blogpost summarizes my findings and thoughts. Bitcoin transactions – recap Every bitcoin transaction creates outputs (called transaction outputs, sometimes called txout) from one or more transaction inputs. All except one type of these transaction output types will create spendable outputs (called unspent transaction outputs – UTXO), the type that behaves differently is OP_RETURN The UTXO are tracked and stored by every full node (btcd or bitcoin-core/satoshi client).

Add code coverage metrics to your maven project

While working on the bitcoinj project I have added support for code coverage collection and tracking. This post summarizes steps you have to take to add that for your own maven projects. Figure out what type of code coverage you want For the bitcoinj library it is important to have a “unit test coverage” - it works by verifying which parts of the source code are reached during unit testing phase during build process.

My Experiences from ASCIIHack Wrocław

Last week I have attended event called “#asciihack Wroclaw” held by guys running HackKRK ( in Wrocław. The idea of the event was to create an ASCII based game in a day, here’s how it look at similar event held in Kraków: Most of the people attending were developing their games in Ruby, and only 2 teams decided to make them with Java. My team (me and Marcin Cichocki) decided to use very nice ASCII game library called AsciiPanel - https://github.

Max Java String Length

I was wondering about what would be the maximum String length in Java, and the funny thing is that Java’s Strings are Arrays that are indexed by int. So the maximum String length is 2^31 - 1 And this is true for any Java Array: