2008-11-262011-08-06 by J. Pablo Fernández

Printing the class-path in Clojure

Let’s compare how we print the class-path in Clojure and how we do it on Java.

(println (seq (.getURLs (java.lang.ClassLoader/getSystemClassLoader))))

In Java:

import java.net.URL;
import java.net.URLClassLoader;

public class PrintClasspath {
    public static void main(String[] args) {
        //Get the System Classloader
        ClassLoader sysClassLoader = ClassLoader.getSystemClassLoader();

        //Get the URLs
        URL[] urls = ((URLClassLoader)sysClassLoader).getURLs();

        for(int i=0; i&lt; urls.length; i++)
        {
            System.out.println(urls[i].getFile());
        }
    }
}

To be fair, the output is not the same, but the effect is.

9 Replies to “Printing the class-path in Clojure”

Matt says:

2010-03-10 at 05:49
Cool one liner. I’m just starting in on Clojure and played around until I could get the Clojure version to print in the same format as your Java version:
```
(doseq [url (seq (.getURLs (java.lang.ClassLoader/getSystemClassLoader)))]
  (println (.getFile url)))
```
Love it!
.-= Matt´s last blog: The super easy way to use Emacs and Slime with Clojure =-.
Reply
Martin says:

2011-01-29 at 22:47
This might not work in all cases.
You could also want:
```
(import 'clojure.pprint)
(pprint (seq (.getURLs (->  (Thread.currentThread)  (.getContextClassLoader)))))
```
Reply
1. Martin says:
  
  2011-02-04 at 00:08
  Sorry:
```
(use 'clojure.pprint)
(import 'java.lang.Thread)
(pprint (seq (.getURLs (-> (Thread/currentThread) (.getContextClassLoader)))))
```
  Reply
  1. Eugene Koontz (@hadooplearnings) says:
    
    2011-12-16 at 20:10
    Martin: syntactic variant on your example:
    
    (use 'clojure.pprint) (import 'java.lang.Thread) (-> (Thread/currentThread) (.getContextClassLoader) (.getURLs) (seq) (pprint))
  2. Eugene Koontz (@hadooplearnings) says:
    
    2011-12-16 at 20:15
    
    My code got messed with by WordPress and got quotes changed to backticks :( Don’t know how to format code in my comment, sorry.
  3. Pablo says:
    
    2011-12-16 at 20:50
    
    I fixed it, thanks for the code.
sticker printing says:

2011-03-23 at 21:59

this code worked fine with the older version of clojure. I tried it with the newer one but unfortunately, it didn’t work out. What could be the issue??

Reply
1. Pablo says:
  
  2011-08-20 at 08:06
  
  It works for me in Clojure 1.2.1, what error are you getting?
  
  Reply
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9 Replies to “Printing the class-path in Clojure”

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