Re: How to find a .class file in a bunch of JARs?

Abhijat Vatsyayan <>
Wed, 06 Aug 2008 21:34:37 -0400
<489a512d$0$29512$> wrote:

On Aug 6, 5:37 pm, Abhijat Vatsyayan <> wrote:

laredotornado wrote:

I'm on Solaris 9. Does anyone know of a way to search through JAR
files (all of which are in the same directory) to find a class
"my.class" without having to unzip each file?
Thanks, - Dave

While on unix I will almost always use the shell, here is a quick and
dirty java based approach -


import java.util.Collection;
import java.util.Enumeration;
import java.util.LinkedList;
import java.util.StringTokenizer;

public class ResourceFinder
        private File dir ;
        private ClassLoader classLoader ;
        ResourceFinder(String dir) throws MalformedURLException
                this.dir = new File(dir);
                initSelf() ;
        private void initSelf() throws MalformedURLException
                FileFilter fileFilter = new filter();
                File[] jarFiles = dir.listFiles(fileFilter);
                URL[] jarURLs = new URL[jarFiles.length];
                for (int i = 0; i < jarFiles.length; i++)
                        File jarFile = jarFiles[i];
                        jarURLs[i] = jarFile.toURL();
                classLoader = new URLClassLoader(jarURLs, null);
        public Collection<String> getJarsContainingClass(String fqClassname)
throws IOException
                String resName = fqClassname.replace('.', '/')+".class";
                Collection<String> jarFiles = new LinkedList<String>();
                Enumeration<URL> urls = classLoader.getResources(resName);
                while (urls.hasMoreElements())
                        URL url = urls.nextElement();
                return jarFiles;
        private static String stringForm(URL jarURL)
                String jarPath = jarURL.toExternalForm();
                StringTokenizer st = new StringTokenizer(jarPath, "!");
                return st.nextToken();
        class filter implements FileFilter
                public boolean accept(File pathname)
                                return false;
                        return pathname.getName().endsWith(".jar");
         * args[0] is the directory containing jars , args[1] is the fully
qualified classname
         * @param args
        public static void main(String[] args)
                        String dir = args[0];
                        String clsName = args[1];
                        ResourceFinder finder = new ResourceFinder(dir);
                        Collection<String> urls = finder.getJarsContainingClass(clsName);
                        for (String url : urls)
                                System.out.println("[ResourceFinder::main()] "+url);
                catch(Exception e)


I like JWhich better.

Sure, you can say it should be in classpath. But that's the point. You
may have dozens of jars with the same class and you want to know which
one exactly you are using inside your Java environment.


I assumed that the class was not in the classpath. Think of this as a
lazy way to read jars file contents which replaces the unix shell
scripts (not that there is any reason to :-) ).

Moreover, I don't think the original post said anything about figuring
out which specific class file (from which URL/jar/dir) was being used in
a context. Figuring that out is just as simple.


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