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From: Steven Simpson <ss@domain.invalid>
Newsgroups: comp.lang.java.programmer
Subject: Re: get path of a Jar file
Date: Mon, 24 Oct 2011 21:07:18 +0100
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On 22/10/11 10:54, Philipp Kraus wrote:
> String l_jarfile = 
> Class.forName("class_within_the_jar").getResource("").toString();
> l_jarfile        = l_jarfile.substring(9, 
> l_jarfile.lastIndexOf(".jar!")) + ".jar";
>
> This does not work on MS Windows systems (unix and OSX work correct 
> with this code).
> If the Jar files is stored under a path like "C:\Users\myuser\Java 
> Files\myjar.jar" (with a space)
> the JarFile-Object can't locate the file, because the space within the 
> directory is changed to %20

Leaving aside the good questions of why, and whether these magic 
constants are a good thing, I will address the decoding of % sequences: 
Create a java.net.URI from the string, then create a java.io.File from 
the URI.

import java.net.*;
import java.io.*;

public class GetPath {
     public static void main(String[] args) throws Exception {
         Class<?>  clazz = Class.forName(args[0]);
         URL clazzRes = clazz.getResource("");
         String loc = clazzRes.toString();
         System.out.println("Resource: " + loc);
         URI stripped =
             URI.create(loc.substring(4, loc.lastIndexOf(".jar!") + 4));
         System.out.println("Stripped: " + stripped);
         File result = new File(stripped);
         System.out.println("Result: " + result);
     }
}

Lots of result checking omitted.

-- 
ss at comp dot lancs dot ac dot uk