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

Yes, you can use URLClassLoader.. see example here. Doesn't use reflection.

-- edit --

Copying example from the link as suggested.

import javax.naming.*;
import java.util.Hashtable;
import java.net.URLClassLoader;
import java.net.URL;
import java.net.MalformedURLException;

public class ChangeLoader {

    public static void main(String[] args) throws MalformedURLException {
    if (args.length != 1) {
        System.err.println("usage: java ChangeLoader codebase_url");
        System.exit(-1);
    }

    String url = args[0];
    ClassLoader prevCl = Thread.currentThread().getContextClassLoader();

    // Create class loader using given codebase
    // Use prevCl as parent to maintain current visibility
    ClassLoader urlCl = URLClassLoader.newInstance(new URL[]{new URL(url)}, prevCl);

        try {
        // Save class loader so that we can restore later
            Thread.currentThread().setContextClassLoader(urlCl);

        // Expect that environment properties are in
        // application resource file found at "url"
        Context ctx = new InitialContext();

        System.out.println(ctx.lookup("tutorial/report.txt"));

        // Close context when no longer needed
        ctx.close();
    } catch (NamingException e) {
        e.printStackTrace();
        } finally {
            // Restore
            Thread.currentThread().setContextClassLoader(prevCl);
        }
    }
}