Can a directory be added to the class path at runtime?

Question

In order to better understand how things works in Java, I\'d like to know if I can dynamically add, at runtime, a directory to the class path.

For example, if I laun

Answer 1

Update 2014: this is the code from the accepted answer, by Jonathan Spooner from 2011, slightly rewritten to have Eclipse's validators no longer create warnings (deprecation, rawtypes)

//need to do add path to Classpath with reflection since the URLClassLoader.addURL(URL url) method is protected:
public static void addPath(String s) throws Exception {
    File f = new File(s);
    URI u = f.toURI();
    URLClassLoader urlClassLoader = (URLClassLoader) ClassLoader.getSystemClassLoader();
    Class urlClass = URLClassLoader.class;
    Method method = urlClass.getDeclaredMethod("addURL", new Class[]{URL.class});
    method.setAccessible(true);
    method.invoke(urlClassLoader, new Object[]{u.toURL()});
}