Filed under Java

Java on iPhone or iPad

What options do I have to make my Java application working on the iPhone? It should not be necessary to jailbreak the phone. Also UI is not necessary for now although e.g. codenameone seems to support it. My application it not a complicated one, but uses Java 1.5 (generics etc) and e.g. memory mapped files. … Continue reading

Make Your Dijkstra Faster

Today I did a bit of research for GraphHopper and I stumbled over yet another minor trick which could speed up the execution of the Dijkstra algorithm. Let me shortly introduce this shortest path algorithm: If you need the path (and not only the shortest path tree) you will give the method an additional toNode … Continue reading

Failed Experiment: Memory Efficient Spatial Hashtable

The Background of my Idea The idea is to use a hash table for points (aka HashMap in Java) and try to implement neighbor searches. First of all you’ll need to understand what a spatial key is. Here you can read the details, but in short it is a binary Geohash where you avoid the memory … Continue reading

Spatial Keys – Memory Efficient Geohashes

When you are operating on geographical data you’ll use latitude and longitude to specify a location somewhere on earth. To look up some associated information or if you want to do neighborhood searches you could create R-trees, quad-trees or similar spatial data structures to make them efficient. Some people are using Geohashes instead because then … Continue reading

Free Online Graph Theory Books and Resources

A link compilation of some Hackernews and Stackoverflow posts and a longish personal investigation. The DaMN book and its companion book Graph Theory with Applications, J.A. Bondy and U.S.R. Murty Graph Theory, Reinhard Diestel Graph Theory Tutorials Digraphs: Theory, Algorithms and Applications, 1st Edition Wikipedia – Graph Algorithms Algorithms and Complexity, Herbert S. Wilf Lecture … Continue reading