Printing the class-path in Clojure

November 26, 2008

Printing the class-path in Clojure

Pablo Fernandez

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&amp;lt; urls.length; i++)
        {
            System.out.println(urls[i].getFile());
        }
    }
}

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

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

Matt

2010-03-10
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 =-.

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Martin

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

2011-03-23

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??

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1. Pablo
  
  2011-08-20
  
  It works for me in Clojure 1.2.1, what error are you getting?
  
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