Sven Woltmann

color-thief-java. Grabs the dominant color or a representative color palette from an image. A very fast Java port of Lokesh Dhakar's JavaScript version.

hexagonal-architecture-java. This repository contains a sample Java REST application implemented according to hexagonal architecture.

pathfinding. Source code for the HappyCoders.eu articles on pathfinding and shortest path algorithms (Dijkstra, A*, Bellman-Ford, Floyd-Warshall).

binary-tree. Source Code for HappyCoders.eu article series on tree data structures (binary tree, binary search tree, AVL tree, red-black tree).

sorting-algorithms-ultimate-guide. Sorting algorithm source codes + ultimate test to compare the performance of all algorithms. For my HappyCoders.eu article.

o-notation-and-time-complexity. Code examples demonstrating the complexity classes O(1), O(log n), O(n), O(n log n), O(n²).

structured-concurrency. Demo code showing how to use Java's StructuredTaskScope

advent-of-code-2022. Advent of Code 2022 – Object-Oriented Solutions in Java: https://www.happycoders.eu/algorithms/advent-of-code-2022/

filechannel-bytebuffer-memory-mapped-io-locks. Demos for writing and reading files with FileChannel and ByteArray. Tests for write speed with RandomAccessFile, FileChannel, heap buffer, native buffer, memory-mapped buffer, and FileOutputStream.

virtual-threads. Demo code showing how to use Java's virtual threads.

stream-gatherers. Demo code for Stream Gatherers presentation

virtual-threads-spring. Spring demo application to compare controllers using CompletableFuture vs. virtual threads.

binary-search. Binary search implementation in Java (recursive and iterative). Comparison with linear search. Runtime test of binary and linear search.

ffm-api-demo. Demonstration of Java's Foreign Function & Memory API

internet-address-resolution-spi-jep-418-demo. A rudimentary demonstration on how to use the Internet-Address Resolution SPI defined in JEP 418 introduced in Java 18. Article: https://www.happycoders.eu/java/java-18-features/

java-collections-guide. Java Queue, Deque, Stack and other collections - Ultimate Guide on HappyCoders.eu.

application-cds-demo. A minimal application for demostrating application class-data sharing (AppCDS).

advent-of-code-2015. Advent of Code 2015 – Object-Oriented Solutions in Java: https://www.happycoders.eu/algorithms/advent-of-code-2015/

bytebuffer-demo. This demo shows how a ByteBuffer and its flip() and compact() methods work.

advent-of-code-2025. Advent of Code 2025 – Java 25 Solutions

scoped-values. Demo code showing how to use Java's scoped values

mastering-data-structures-in-java. Quellcode zum Online-Kurs „Mastering Data Structures in Java“

pattern-matching-for-switch. Pattern Matching for Switch Examples

arrays-and-lists. Code accompanying the “Arrays and lists” video series

ultimate-guide-queue-deque-stack. Java Queue, Deque, Stack - Ultimate Guide on HappyCoders.eu

files-structured-data. Source code for my HappyCoders.eu article about writing structured data with DataOutputStream, DataInputStream, ObjectOutputStream and ObjectInputStream.

int-to-string-benchmarks. JMH benchmark tests to find out what is the fastest way to convert an int into a String in Java.

sorting-in-java. Demo code for HappyCoders.eu tutorial about sorting primitives and objects with Java.

happycoders-tutorial-server-setup. Source code for HappyCoders.eu Ansible tutorial.

deep-reflection. How can Java Reflection be used to change the values of Integers and Strings at runtime?

sparse-checkout-demo. Source code for the HappyCoders.eu article about Git Monorepos.

jenkins-tutorial-demo. Code for HappyCoders.eu Jenkins tutorial explaining the installation and major features of Jenkins.

java-kata. Maven project for Java Katas containing only a class, a test class, and dependencies to JUnit, AssertJ, and Mockito

comparator-comparable-compareto. Source code for my HappyCoders.eu article about comparing objects in Java using Comparable, Comparator, compareTo().

string-substring-demo. A demonstration of the String.substring() method and its evolution from Java 1.2 to today.

java-structured-concurrency-demo. Demo code for the HappyCoders.eu article "Structured Concurrency with Java".

string-to-int-benchmarks. JMH benchmark tests to measure the speed of various methods to convert Strings to int / Integer in Java.

project-b. Source code for the HappyCoders.eu article about Git Monorepos.

java-random-demo. Java random number generation demos. Article on HappyCoders.eu.

project-a. Source code for the HappyCoders.eu article about Git Monorepos.

biased-locking. A JMH benchmark demostrating the effects of disabled biased locking in Java 15.