Question

In a Android application I want to use Scanner class to read a list of floats from a text file (it’s a list of vertex coordinates for OpenGL). Exact code is:

Scanner in = new Scanner(new BufferedInputStream(getAssets().open("vertexes.off")));
final float[] vertexes = new float[nrVertexes];
for(int i=0;i<nrVertexFloats;i++){
    vertexes[i] = in.nextFloat();
}

It seems however that this is incredibly slow (it took 30 minutes to read 10,000 floats!) – as tested on the 2.1 emulator. What’s going on?
I don’t remember Scanner to be that slow when I used it on the PC (truth be told I never read more than 100 values before). Or is it something else, like reading from an asset input stream?

Thanks for the help!

Answer 1

Don’t know about Android, but at least in JavaSE, Scanner is slow.

Internally, Scanner does UTF-8 conversion, which is useless in a file with floats.

Since all you want to do is read floats from a file, you should go with the java.io package.

The folks on SPOJ struggle with I/O speed. It’s is a Polish programming contest site with very hard problems. Their difference is that they accept a wider array of programming languages than other sites, and in many of their problems, the input is so large that if you don’t write efficient I/O, your program will burst the time limit.

Of course, I advise against writing your own float parser, but if you need speed, that’s still a solution.