Java: Traversing a File Structure

 import java.io.*;
  
  public class roots {
    public static void visit(File f) {
      System.out.println(f);
    }
  
    public static void walk(File f) {
      visit(f);
      if (f.isDirectory()) {
        String list[] = f.list();
        for (int i = 0; i < list.length; i++)
          walk(new File(f, list[i]));
      }
    }
  
    public static void main(String args[]) {
      File list[] = File.listRoots();
      for (int i = 0; i < list.length; i++) {
        if (list[i].exists())
          walk(list[i]);
        else
          System.err.println("not accessible: "
              + list[i]);
      }
    }
  }

From http://java.sun.com/developer/technicalArticles/Programming/PerfTuning/