code: @SuppressWarnings("unchecked")
  	public <U> List<U> getInstances(String name, Class<U> xface) {
  		List<U> ret = new ArrayList<U>();
  		Class<?>[] classes = getClasses(name);
  		for (Class<?> cl: classes) {
  			if (!xface.isAssignableFrom(cl)) {
  				throw new RuntimeException(cl + " does not implement " + xface);
  			}
  			ret.add((U)ReflectionUtils.newInstance(cl, this));
  		}
  		return ret;
  	}
docs: Get the value of the <code>name</code> property as a <code>List</code>
  of objects implementing the interface specified by <code>xface</code>.
  
  An exception is thrown if any of the classes does not exist, or if it does
  not implement the named interface.
  
  @param name the property name.
  @param xface the interface implemented by the classes named by
  <code>name</code>.
  @return a <code>List</code> of objects implementing <code>xface</code>.