code: public void defineFunction(String prefix, String function, Method method)
              throws NoSuchMethodException {
          if (prefix == null || function == null || method == null) {
              throw new NullPointerException("Null argument for defineFunction");
          }
          if (! Modifier.isStatic(method.getModifiers())) {
              throw new NoSuchMethodException("The method specified in defineFunction must be static: " + method);
          }
          if (function.equals("")) {
              function = method.getName();
         }
          elManager.mapFunction(prefix, function, method);
      }
docs: Define an EL function in the local function mapper.
  @param prefix The namespace for the function or "" for no namesapce.
  @param function The name of the function.
  If empty (""), the method name is used as the function name.
  @param method The <code>java.lang.reflect.Method</code> instance of
  the method that implements the function.
  @throws NullPointerException if any of the arguments is null.
  @throws NoSuchMethodException if the method is not a static method