Quick example of file traversal

FileLister

import java.io.File;

public class FileLister {
   public static void main(String[] args) {
	      list(new File("/"));
	   }
	   
	   /**
	    * Display a list of the specified file and all its descendants.
	    */
	   public static void list(File root) {
	      
	      // We don't expect the caller to be concerned with the level argument, so
	      // we make this method just a wrapper method that is called once.  We
	      // call the helper method that does the real work and prime level to be
	      // 0.
	      list(root, 0);
	   }
	   
	   /**
	    * Display a list of all files in the file system descending from
	    * root, one per line. Files are indented according
	    * to their depth in the hierarchy, as indicated by level.
	    * 
	    * @param root
	    * The root file of this hierarchy.
	    * 
	    * @param level
	    * The number of levels into the overall hierarchy that we have
	    * traversed.
	    */
	   private static void list(File root, int level) {
	      
	      // Print indented filename.  This is a bit tricky, but as level
	      // increases, we print out a space ' ' with increased padding:
	      // %1c, %2c, %3c, and so on. %s displays the string argument.
	      // %n turns into a platform-independent newline. Check out the
	      // Javadoc for formatted printing if you want to know more:
	      //
	      // http://java.sun.com/javase/6/docs/api/java/util/Formatter.html#syntax
	      //
	      // We could do the same thing with a loop.
	      System.out.printf("%" + (level + 1) + "c%s%n", ' ', root.getName());
	      
	      // See if this file is a directory and has any files within it. If
	      // so, each of those files becomes the root of a hierarchy one level
	      // deeper.
	      File[] contents = root.listFiles();
	      if (contents != null) {
	         for (int i = 0; i < contents.length; ++i) {
	            list(contents[i], level + 1);
	         }
	      }
	   }
}